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Avian influenza Fact sheet Updated March 2014 Key facts Avian influenza (AI), commonly called bird flu, is an infectious viral disease of birds. Most avian influenza viruses do not infect humans; however some, such as A(H5N1) and A(H7N9), have caused serious infections in people. Outbreaks of AI in poultry may raise global public health concerns due to their effect on poultry populations, their potential to cause serious disease in people, and their pandemic potential. Reports of highly pathogenic AI epidemics in poultry, such as A(H5N1), can seriously impact local and global economies and international trade. The majority of human cases of A(H5N1) and A(H7N9) infection have been associated with direct or indirect contact with infected live or dead poultry. There is no evidence that the disease can be spread to people through properly cooked food. Controlling the disease in animals is the first step in decreasing risks to humans. Avian influenza (AI) is an infectious viral disease of birds (especially wild water fowl such as ducks and geese), often causing no apparent signs of illness. AI viruses can sometimes spread to domestic poultry and cause large-scale outbreaks of serious disease. Some of these AI viruses have also been reported to cross the species barrier and cause disease or subclinical infections in humans and other mammals. AI viruses are divided into 2 groups based on their ability to cause disease in poultry: high pathogenicity or low pathogenicity. Highly pathogenic viruses result in high death rates (up to 100% mortality within 48 hours) in some poultry species. Low pathogenicity viruses also cause outbreaks in poultry but are not generally associated with severe disease. Avian influenza A(H5N1) and A(H7N9) background

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compilation of fact sheets from the World Health Organization


Page 1: Who Fact Sheets

Avian influenza

Fact sheet Updated March 2014

Key facts

Avian influenza (AI), commonly called bird flu, is an infectious viral disease of birds. Most avian influenza viruses do not infect humans; however some, such as A(H5N1) and

A(H7N9), have caused serious infections in people. Outbreaks of AI in poultry may raise global public health concerns due to their effect on poultry

populations, their potential to cause serious disease in people, and their pandemic potential. Reports of highly pathogenic AI epidemics in poultry, such as A(H5N1), can seriously impact local

and global economies and international trade. The majority of human cases of A(H5N1) and A(H7N9) infection have been associated with direct

or indirect contact with infected live or dead poultry. There is no evidence that the disease can be spread to people through properly cooked food.

Controlling the disease in animals is the first step in decreasing risks to humans.

Avian influenza (AI) is an infectious viral disease of birds (especially wild water fowl such as ducks and geese), often causing no apparent signs of illness. AI viruses can sometimes spread to domestic poultry and cause large-scale outbreaks of serious disease. Some of these AI viruses have also been reported to cross the species barrier and cause disease or subclinical infections in humans and other mammals.AI viruses are divided into 2 groups based on their ability to cause disease in poultry: high pathogenicity or low pathogenicity. Highly pathogenic viruses result in high death rates (up to 100% mortality within 48 hours) in some poultry species. Low pathogenicity viruses also cause outbreaks in poultry but are not generally associated with severe disease.

Avian influenza A(H5N1) and A(H7N9) background

The A(H5N1) virus subtype, a highly pathogenic AI virus, first infected humans in 1997 during a poultry outbreak in Hong Kong SAR, China. Since its widespread re-emergence in 2003 and 2004, this avian virus has spread from Asia to Europe and Africa and has become entrenched in poultry in some countries, resulting in millions of poultry infections, several hundred human cases, and many human deaths. Outbreaks in poultry have seriously impacted livelihoods, the economy and international trade in affected countries.The A(H7N9) virus subtype, a low pathogenic AI virus, first infected 3 humans – 2 residents of the city of Shanghai and 1 resident of Anhui province - in March 2013. No cases of A(H7N9) outside of China have been reported. Containment measures, including the closure of live bird markets for several months, have impacted the agriculture sectors of affected countries and international trade. Continued surveillance for A(H7N9) will be necessary to detect and control the spread of the virus.Ongoing circulation of A(H5N1) and A(H7N9) viruses in poultry, especially where endemic, continues to pose threats to public health, as these viruses have both the potential to cause serious disease in people and may have the potential to change into a form that is more transmissible among humans.

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Other influenza virus subtypes also circulate in poultry and other animals, and may also pose potential threats to public health.

Avian influenza A(H5N1) and A(H7N9) infections and clinical features in humans

The case fatality rate for A(H5N1) and A(H7N9) virus infections in people is much higher compared to that of seasonal influenza infections. The A(H7N9) virus particularly affects people with underlying medical conditions.

Clinical features

In many patients, the disease caused by the A(H5N1) virus follows an unusually aggressive clinical course, with rapid deterioration and high fatality. Like most emerging disease, A(H5N1) influenza in humans is not well understood.The incubation period for A(H5N1) avian influenza may be longer than that for normal seasonal influenza, which is around 2 to 3 days. Current data for A(H5N1) infection indicate an incubation period ranging from 2 to 8 days and possibly as long as 17 days. Current data for A(H7N9) infection indicate an incubation period ranging from 2 to 8 days, with an average of five days.1 WHO currently recommends that an incubation period of 7 days be used for field investigations and the monitoring of patient contacts.Initial symptoms include high fever, usually with a temperature higher than 38°C, and other influenza-like symptoms (cough or sore throat). Diarrhea, vomiting, abdominal pain, chest pain, and bleeding from the nose and gums have also been reported as early symptoms in some patients.One feature seen in many patients is the development of lower respiratory tract early in the illness. Respiratory distress, a hoarse voice, and a crackling sound when inhaling are commonly seen. Sputum production is variable and sometimes bloody.2Complications of A(H5N1) and A(H7N9) infection include hypoxemia, multiple organ dysfunction, and secondary bacterial and fungal infections.3

Antiviral treatment

Evidence suggests that some antiviral drugs, notably oseltamivir, can reduce the duration of viral replication and improve prospects of survival.In suspected cases, oseltamivir should be prescribed as soon as possible (ideally, within 48 hours following symptom onset) to maximize its therapeutic benefits. However, given the significant mortality currently associated with A(H5N1) and A(H7N9) infection and evidence of prolonged viral replication in this disease, administration of the drug should also be considered in patients presenting later in the course of illness. The use of corticosteroids is not recommended.In cases of severe infection with the A(H5N1) or A(H7N9) virus, clinicians may need to consider increasing the recommended daily dose or/and the duration of treatment.In severely ill A(H5N1) or A(H7N9) patients or in patients with severe gastrointestinal symptoms, drug absorption may be impaired. This possibility should be considered when managing these patients.4 Moreover, most A(H5N1) and A(H7N9) viruses are predicated to be resistant to adamantine antiviral drugs, which are therefore not recommended for use.

Risk factors for human infection

The primary risk factor for human infection appears to be direct or indirect exposure to infected live or dead poultry or contaminated environments, such as live bird markets. Controlling circulation of the A(H5N1) and A(H7N9) viruses in poultry is essential to reducing the risk of human infection.

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Given the persistence of the A(H5N1) and A(H7N9) viruses in some poultry populations, control will require long-term commitments from countries and strong coordination between animal and public health authorities.There is no evidence to suggest that the A(H5N1)and A(H7N9) viruses can be transmitted to humans through properly prepared poultry or eggs. A few A(H5N1) human cases have been linked to consumption of dishes made of raw, contaminated poultry blood. However, slaughter, defeathering, handling carcasses of infected poultry, and preparing poultry for consumption, especially in household settings, are likely to be risk factors.

Human pandemic potential

Influenza pandemics (outbreaks that affect a large proportion of the world due to a novel virus) are unpredictable but recurring events that can have health, economic and social consequences worldwide. An influenza pandemic occurs when key factors converge: an influenza virus emerges with the ability to cause sustained human-to-human transmission, and the human population has little to no immunity against the virus. With the growth of global trade and travel, a localized epidemic can transform into a pandemic rapidly, with little time to prepare a public health response.The A(H5N1) and A(H7N9) AI viruses remain two of the influenza viruses with pandemic potential, because they continue to circulate widely in some poultry populations, most humans likely have no immunity to them, and they can cause severe disease and death in humans.However, whether the influenza A(H7N9) virus could actually cause a pandemic is unknown. Experience has shown that some animal influenza viruses that have been found to occasionally infect people have not gone on to cause a pandemic while others have done so. Surveillance and the investigations now underway will provide some of the information needed to make this determination.In addition to A(H5N1) and A(H7N9), other animal influenza virus subtypes reported to have infected people include avian H9, and swine H1 and H3 viruses. H2 viruses may also pose a pandemic threat. Therefore, pandemic planning should consider risks of emergence of a variety of influenza subtypes from a variety of sources.

WHO response

WHO, in its capacity for providing leadership on global health matters, is monitoring avian influenza very closely, developing and adjusting appropriate interventions in collaboration with its partners. Such partners include animal health agencies and national veterinary authorities responsible for the control and prevention of animal diseases, including influenza.Specifically, WHO, the World Organisation for Animal Health (OIE), and the Food and Agriculture Organization (FAO) collaborate through a variety of mechanisms to track and assess the risk from animal influenza viruses of public health concern, and to address these risks at the human animal interface wherever in the world they might occur. In short, WHO is monitoring the situation as it evolves, and as more information becomes available, will revise its guidance and actions accordingly.

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Fact sheet N°107Updated July 2015

Key facts

Cholera is an acute diarrhoeal disease that can kill within hours if left untreated. Researchers have estimated that there are 1.4 to 4.3 million cases, and 28 000 to 142 000 deaths

worldwide1 due to cholera every year. Up to 80% of cases can be successfully treated with oral rehydration salts. Provision of safe water and sanitation is critical to control cholera and other waterborne

diseases. Oral cholera vaccines are an additional way to control cholera, but should not replace

conventional control measures.

Cholera is an acute diarrhoeal infection caused by ingestion of food or water contaminated with the bacterium Vibrio cholerae. Researchers have estimated that every year, there are roughly 1.4 to 4.3 million cases, and 28 000 to 142 000 deaths per year worldwide1 due to cholera. The short incubation period of 2 hours to 5 days, is 1 factor that triggers the potentially explosive pattern of outbreaks.


Cholera is an extremely virulent disease. It affects both children and adults and can kill within hours.About 80% of people infected with V. cholerae do not develop any symptoms, although the bacteria are present in their faeces for 1-10 days after infection and are shed back into the environment, potentially infecting other people.Among people who develop symptoms, 80% have mild or moderate symptoms, while around 20% develop acute watery diarrhoea with severe dehydration. This can lead to death if left untreated.


During the 19th century, cholera spread across the world from its original reservoir in the Ganges delta in India. Six subsequent pandemics killed millions of people across all continents. The current (seventh) pandemic started in South Asia in 1961, and reached Africa in 1971 and the Americas in 1991. Cholera is now endemic in many countries.

Vibrio cholerae strainsTwo serogroups of V. cholerae – O1 and O139 – cause outbreaks. V. cholerae O1 causes the majority of outbreaks, while O139 – first identified in Bangladesh in 1992 – is confined to South-East Asia.Non-O1 and non-O139 V. cholerae can cause mild diarrhoea but do not generate epidemics.

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Recently, new variant strains have been detected in several parts of Asia and Africa. Observations suggest that these strains cause more severe cholera with higher case fatality rates. Careful epidemiological monitoring of circulating strains is recommended.The main reservoirs of V. cholerae are people and aquatic sources such as brackish water and estuaries, often associated with algal blooms. Recent studies indicate that global warming creates a favourable environment for the bacteria.

Risk factors and disease burden

Cholera transmission is closely linked to inadequate environmental management. Typical at-risk areas include peri-urban slums, where basic infrastructure is not available, as well as camps for internally displaced persons or refugees, where minimum requirements of clean water and sanitation are not met.The consequences of a humanitarian crisis – such as disruption of water and sanitation systems, or the displacement of populations to inadequate and overcrowded camps – can increase the risk of cholera transmission should the bacteria be present or introduced. Dead bodies have never been reported as the source of epidemics.Cholera remains a global threat to public health and a key indicator of lack of social development.The number of cholera cases reported to WHO continues to be high. During 2013, a total of 129 064 cases were notified from 47 countries, including 2102 deaths. The discrepancy between those figures and the estimated burden of the disease is due to the fact that many cases are not recorded for due to limitations in surveillance systems and fear of trade and travel sanctions.

Prevention and control

A multidisciplinary approach is key for reducing cholera outbreaks, controlling cholera in endemic areas and reducing deaths.

Water and sanitation interventions

The long-term solution for cholera control (which benefits all diseases spread by the fecal-oral route) lies in economic development and universal access to safe drinking water and adequate sanitation, which is key in preventing both epidemic and endemic cholera.Actions targeting environmental conditions include:

the development of piped water systems with water treatment facilities (chlorination); interventions at the household level (water filtration, water chemical or solar disinfection, safe water

storage containers); and as well as the construction of systems for sewage disposal and latrines.

Most of those interventions require substantial long term investments and high maintenance costs which are difficult to fund and sustain by the least developed countries, where they are also most needed.


Cholera is an easily treatable disease. Up to 80% of people can be treated successfully through prompt administration of oral rehydration salts (WHO/UNICEF ORS standard sachet). Very severely dehydrated patients require the administration of intravenous fluids. These patients also need appropriate antibiotics to diminish the duration of diarrhoea, reduce the volume of rehydration fluids needed, and shorten the duration of V. cholerae excretion. Mass administration of antibiotics

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is not recommended, as it has no effect on the spread of cholera and contributes to increasing antimicrobial resistance.In order to ensure timely access to treatment, cholera treatment centres (CTCs) should be set up within the affected communities. With proper treatment, the case fatality rate should remain below 1%.


Under the International Health Regulations, notification of all cases of cholera is no longer mandatory. However, public health events involving cholera must always be assessed against the criteria provided in the Regulations to determine whether there is a need for official notification.Local capacities for improving diagnosis, and for collecting, compiling and analysing data, need to be strengthened so that vulnerable populations living in high-risk areas can be identified in order to benefit from comprehensive control activities. Cholera surveillance should be part of an integrated disease surveillance system that includes feedback at the local level and information-sharing at the global level.

Social mobilisation

Health education campaigns, adapted to local culture and beliefs, should promote the adoption of appropriate hygiene practices such as hand-washing with soap, safe preparation and storage of food and breastfeeding.Awareness campaigns during outbreaks also encourage people with symptoms to seek immediate health care. The campaigns should use modern communication channels (mobile phones, smartphones, social media, etc.) and adapted to local cultures. The use of qualitative methods of analysis, to help adapt messages to local culture and beliefs, is also encouraged.

Oral cholera vaccines

Currently there are 2 WHO pre-qualified oral cholera vaccines (OCVs) (Dukoral® and Shanchol®). Both vaccines have been used in mass vaccination campaigns with WHO support. Their use has enabled evidence to be collected on the effectiveness and feasibility on implementation of oral cholera vaccination campaigns as a public health tool in protecting populations at high risk of cholera.Dukoral® is administered to adults and children aged >6 years in 2 doses; and to children aged >2 years and <6 years in 3 doses. Protection can be expected 1 week after the last dose. Field trials in Bangladesh and Peru have shown that this vaccine is safe and confers 85% protection for 4–6 months in all age groups. This vaccine is not licensed for use in children aged <2 years.Shanchol’s immunization schedule is 2 doses given at an interval of 2 weeks for those aged >1 year. Shanchol® has provided longer term protection than Dukoral® in children aged <5 years, and therefore does not require a booster dose after 6 months in this age group, unlike Dukoral®. Shanchol® provided 67% protection against clinically significant V. cholerae O1 cholera in an endemic area for at least 2 years after vaccination. A field trial in Kolkata, India obtained protective efficacy (65%) of the vaccine up to 5 years.An OCV stockpile of 2 million doses was formally established mid-2013 for outbreak control and emergencies. The OCV stockpile was created on the principle that vaccines have a role in the prevention and control of cholera when used in conjunction with accessible healthcare and improvements in water and sanitation.In November 2013, the GAVI board approved a contribution to the global cholera vaccine stockpile for epidemic and endemic settings, for 2014-2018. The objectives of the GAVI investment are to:

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1. break the current cycle of low demand–low supply, significantly increasing global OCV production and availability;

2. reduce the impact of cholera outbreaks; and3. strengthen the evidence base for periodic pre-emptive campaigns.4. As of June 2015, about 2 million doses of OCV have been shipped from the stockpile in

various settings, either in the form of reactive campaigns in areas experiencing an outbreak or pre-emptive vaccination campaigns among populations at elevated risk for cholera (“hotspots”), or at heightened vulnerability during an humanitarian crisis.

Impact on cholera burden or transmission was significant in all endemic, outbreak and emergency settings. Furthermore, contrary to earlier concerns, the communities readily accepted the vaccines and high vaccine coverage were reported. No serious adverse effects have been reported so far.

Travel and trade

Today, no country requires proof of cholera vaccination as a condition for entry. Past experience shows that quarantine measures and embargoes on the movement of people and goods are unnecessary. Import restrictions on food produced using good manufacturing practices, based on the sole fact that cholera is epidemic or endemic in a country, are not justified.Countries neighbouring cholera-affected areas are encouraged to strengthen disease surveillance and national preparedness to rapidly detect and respond to outbreaks should cholera spread across borders. Further, information should be provided to travellers and the community on the potential risks and symptoms of cholera, together with precautions to avoid cholera, and when and where to report cases.

WHO response

Through the WHO Global Task Force on Cholera Control, WHO works to: support the design and implementation of global strategies to contribute to capacity

development for cholera prevention and control globally; provide a forum for technical exchange, coordination, and cooperation on cholera-related

activities to strengthen countries’ capacity to prevent and control cholera; support countries for the implementation of effective cholera control strategies and

monitoring of progress; disseminate technical guidelines and operational manuals; support the development of a research agenda with emphasis on evaluating innovative

approaches to cholera prevention and control in affected countries; increase the visibility of cholera as an important global public health problem through the

dissemination of information about cholera prevention and control, and conducting advocacy and resource mobilization activities to support cholera prevention and control at national, regional, and global levels.

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Dengue and severe dengue

Fact sheet N°117Updated May 2015

Key facts

Dengue is a mosquito-borne viral infection. The infection causes flu-like illness, and occasionally develops into a potentially lethal

complication called severe dengue. The global incidence of dengue has grown dramatically in recent decades. About half of the world's population is now at risk. Dengue is found in tropical and sub-tropical climates worldwide, mostly in urban and semi-urban

areas. Severe dengue is a leading cause of serious illness and death among children in some Asian and

Latin American countries. There is no specific treatment for dengue/ severe dengue, but early detection and access to

proper medical care lowers fatality rates below 1%. Dengue prevention and control solely depends on effective vector control measures.

Dengue is a mosquito-borne viral disease that has rapidly spread in all regions of WHO in recent years. Dengue virus is transmitted by female mosquitoes mainly of the species Aedes aegypti and, to a lesser extent, A. albopictus. The disease is widespread throughout the tropics, with local variations in risk influenced by rainfall, temperature and unplanned rapid urbanization.Severe dengue (also known as Dengue Haemorrhagic Fever) was first recognized in the 1950s during dengue epidemics in the Philippines and Thailand. Today, severe dengue affects most Asian and Latin American countries and has become a leading cause of hospitalization and death among children in these regions.There are 4 distinct, but closely related, serotypes of the virus that cause dengue (DEN-1, DEN-2, DEN-3 and DEN-4). Recovery from infection by one provides lifelong immunity against that particular serotype. However, cross-immunity to the other serotypes after recovery is only partial and temporary. Subsequent infections by other serotypes increase the risk of developing severe dengue.

Global burden of dengue

The incidence of dengue has grown dramatically around the world in recent decades. The actual numbers of dengue cases are underreported and many cases are misclassified. One recent estimate indicates 390 million dengue infections per year (95% credible interval 284–528 million), of which 96 million (67–136 million) manifest clinically (with any severity of disease).1 Another study, of the

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prevalence of dengue, estimates that 3900 million people, in 128 countries, are at risk of infection with dengue viruses.2

Member States in 3 WHO regions regularly report the annual number of cases. In 2010, nearly 2.4 million cases were reported. Although the full global burden of the disease is uncertain, the initiation of activities to record all dengue cases partly explains the sharp increase in the number of cases reported in recent years.Other features of the disease include its epidemiological patterns, including hyper-endemicity of multiple dengue virus serotypes in many countries and the alarming impact on both human health and the global and national economies.Before 1970, only 9 countries had experienced severe dengue epidemics. The disease is now endemic in more than 100 countries in the WHO regions of Africa, the Americas, the Eastern Mediterranean, South-East Asia and the Western Pacific. The America, South-East Asia and Western Pacific regions are the most seriously affected.Cases across the Americas, South-East Asia and Western Pacific exceeded 1.2 million in 2008 and over 3 million in 2013 (based on official data submitted by Member States). Recently the number of reported cases has continued to increase. In 2013, 2.35 million cases of dengue were reported in the Americas alone, of which 37 687 cases were of severe dengue.Not only is the number of cases increasing as the disease spreads to new areas, but explosive outbreaks are occurring. The threat of a possible outbreak of dengue fever now exists in Europe and local transmission of dengue was reported for the first time in France and Croatia in 2010 and imported cases were detected in 3 other European countries. In 2012, an outbreak of dengue on the Madeira islands of Portugal resulted in over 2000 cases and imported cases were detected in mainland Portugal and 10 other countries in Europe.In 2013, cases have occurred in Florida (United States of America) and Yunnan province of China. Dengue also continues to affect several South American countries, notably Costa Rica, Honduras and Mexico. In Asia, Singapore has reported an increase in cases after a lapse of several years and outbreaks have also been reported in Laos. In 2014, trends indicate increases in the number of cases in the People's Republic of China, the Cook Islands, Fiji, Malaysia and Vanuatu, with Dengue Type 3 (DEN 3) affecting the Pacific Island countries after a lapse of over 10 years. Dengue was also reported in Japan after a lapse of over 70 years. In 2015 an increase in the number of cases was reported in Brazil and several neighbouring countries. The Pacific island countries of Fiji, Tonga and French Polynesia have continued to record cases.An estimated 500 000 people with severe dengue require hospitalization each year, a large proportion of whom are children. About 2.5% of those affected die.


WHO/TDR/StammersThe Aedes aegypti mosquito is the primary vector of dengue. The virus is transmitted to humans through the bites of infected female mosquitoes. After virus incubation for 4–10 days, an infected mosquito is capable of transmitting the virus for the rest of its life.Infected humans are the main carriers and multipliers of the virus, serving as a source of the virus for uninfected mosquitoes. Patients who are already infected with the dengue virus can transmit the infection (for 4–5 days; maximum 12) via Aedesmosquitoes after their first symptoms appear.The Aedes aegypti mosquito lives in urban habitats and breeds mostly in man-made containers. Unlike other mosquitoes Ae. aegypti is a day-time feeder; its peak biting periods are early in the morning and in the evening before dusk. Female Ae. aegyptibites multiple people during each feeding period.

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Aedes albopictus, a secondary dengue vector in Asia, has spread to North America and Europe largely due to the international trade in used tyres (a breeding habitat) and other goods (e.g. lucky bamboo). Ae. albopictus is highly adaptive and, therefore, can survive in cooler temperate regions of Europe. Its spread is due to its tolerance to temperatures below freezing, hibernation, and ability to shelter in microhabitats.


Dengue fever is a severe, flu-like illness that affects infants, young children and adults, but seldom causes death.Dengue should be suspected when a high fever (40°C/104°F) is accompanied by 2 of the following symptoms: severe headache, pain behind the eyes, muscle and joint pains, nausea, vomiting, swollen glands or rash. Symptoms usually last for 2–7 days, after an incubation period of 4–10 days after the bite from an infected mosquito.Severe dengue is a potentially deadly complication due to plasma leaking, fluid accumulation, respiratory distress, severe bleeding, or organ impairment. Warning signs occur 3–7 days after the first symptoms in conjunction with a decrease in temperature (below 38°C/100°F) and include: severe abdominal pain, persistent vomiting, rapid breathing, bleeding gums, fatigue, restlessness and blood in vomit. The next 24–48 hours of the critical stage can be lethal; proper medical care is needed to avoid complications and risk of death.


There is no specific treatment for dengue fever.For severe dengue, medical care by physicians and nurses experienced with the effects and progression of the disease can save lives – decreasing mortality rates from more than 20% to less than 1%. Maintenance of the patient's body fluid volume is critical to severe dengue care.


There is no vaccine to protect against dengue. However, major progress has been made in developing a vaccine against dengue/severe dengue. Three tetravalent live-attenuated vaccines are under development in phase II and phase III clinical trials, and 3 other vaccine candidates (based on subunit, DNA and purified inactivated virus platforms) are at earlier stages of clinical development. WHO provides technical advice and guidance to countries and private partners to support vaccine research and evaluation.

Prevention and control

WHO/TDR/CrumpAt present, the only method to control or prevent the transmission of dengue virus is to combat vector mosquitoes through:

preventing mosquitoes from accessing egg-laying habitats by environmental management and modification;

disposing of solid waste properly and removing artificial man-made habitats; covering, emptying and cleaning of domestic water storage containers on a weekly basis; applying appropriate insecticides to water storage outdoor containers; using of personal household protection such as window screens, long-sleeved clothes,

insecticide treated materials, coils and vaporizers;

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improving community participation and mobilization for sustained vector control; applying insecticides as space spraying during outbreaks as one of the emergency vector-

control measures; active monitoring and surveillance of vectors should be carried out to determine

effectiveness of control interventions. WHO response WHO responds to dengue in the following ways: supports countries in the confirmation of outbreaks through its collaborating network of

laboratories; provides technical support and guidance to countries for the effective management of

dengue outbreaks; supports countries to improve their reporting systems and capture the true burden of the

disease; provides training on clinical management, diagnosis and vector control at the regional level

with some of its collaborating centres; formulates evidence-based strategies and policies; develops new tools, including insecticide products and application technologies; gathers official records of dengue and severe dengue from over 100 Member States; and publishes guidelines and handbooks for case management, dengue prevention and control

for Member States.

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Ebola virus disease

Fact sheet N°103Updated August 2015

Key facts

Ebola virus disease (EVD), formerly known as Ebola haemorrhagic fever, is a severe, often fatal illness in humans.

The virus is transmitted to people from wild animals and spreads in the human population through human-to-human transmission.

The average EVD case fatality rate is around 50%. Case fatality rates have varied from 25% to 90% in past outbreaks.

The first EVD outbreaks occurred in remote villages in Central Africa, near tropical rainforests, but the most recent outbreak in West Africa has involved major urban as well as rural areas.

Community engagement is key to successfully controlling outbreaks. Good outbreak control relies on applying a package of interventions, namely case management, surveillance and contact tracing, a good laboratory service, safe burials and social mobilisation.

Early supportive care with rehydration, symptomatic treatment improves survival. There is as yet no licensed treatment proven to neutralise the virus but a range of blood, immunological and drug therapies are under development.

There are currently no licensed Ebola vaccines but 2 potential candidates are undergoing evaluation.


The Ebola virus causes an acute, serious illness which is often fatal if untreated. Ebola virus disease (EVD) first appeared in 1976 in 2 simultaneous outbreaks, one in Nzara, Sudan, and the other in Yambuku, Democratic Republic of Congo. The latter occurred in a village near the Ebola River, from which the disease takes its name.The current outbreak in West Africa, (first cases notified in March 2014), is the largest and most complex Ebola outbreak since the Ebola virus was first discovered in 1976. There have been more cases and deaths in this outbreak than all others combined. It has also spread between countries starting in Guinea then spreading across land borders to Sierra Leone and Liberia, by air (1 traveller) to Nigeria and USA (1 traveller), and by land to Senegal (1 traveller) and Mali (2 travellers).The most severely affected countries, Guinea, Liberia and Sierra Leone, have very weak health systems, lack human and infrastructural resources, and have only recently emerged from long periods of conflict and instability. On August 8, the WHO Director-General declared the West Africa

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outbreak a Public Health Emergency of International Concern under the International Health Regulations (2005).The virus family Filoviridae includes three genera: Cuevavirus, Marburgvirus, and Ebolavirus. There are five species that have been identified: Zaire, Bundibugyo, Sudan, Reston and Taï Forest. The first three, Bundibugyo ebolavirus, Zaire ebolavirus, and Sudan ebolavirus have been associated with large outbreaks in Africa. The virus causing the 2014 West African outbreak belongs to the Zaire species.


It is thought that fruit bats of the Pteropodidae family are natural Ebola virus hosts. Ebola is introduced into the human population through close contact with the blood, secretions, organs or other bodily fluids of infected animals such as chimpanzees, gorillas, fruit bats, monkeys, forest antelope and porcupines found ill or dead or in the rainforest.Ebola then spreads through human-to-human transmission via direct contact (through broken skin or mucous membranes) with the blood, secretions, organs or other bodily fluids of infected people, and with surfaces and materials (e.g. bedding, clothing) contaminated with these fluids.Health-care workers have frequently been infected while treating patients with suspected or confirmed EVD. This has occurred through close contact with patients when infection control precautions are not strictly practiced.Burial ceremonies in which mourners have direct contact with the body of the deceased person can also play a role in the transmission of Ebola.People remain infectious as long as their blood contains the virus.

Sexual transmission

More surveillance data and research are needed on the risks of sexual transmission, and particularly on the prevalence of viable and transmissible virus in semen over time. In the interim, and based on present evidence, WHO recommends that:

All Ebola survivors and their sexual partners should receive counselling to ensure safe sexual practices until their semen has twice tested negative. Survivors should be provided with condoms.

Male Ebola survivors should be offered semen testing at 3 months after onset of disease, and then, for those who test positive, every month thereafter until their semen tests negative for virus twice by RT-PCR, with an interval of one week between tests.

Ebola survivors and their sexual partners should either:o abstain from all types of sex, oro observe safe sex through correct and consistent condom use until their semen has

twice tested negative. Having tested negative, survivors can safely resume normal sexual practices without fear of

Ebola virus transmission. If an Ebola survivor’s semen has not been tested, he should continue to practise safe sex for

at least 6 months after the onset of symptoms; this interval may be adjusted as additional information becomes available on the prevalence of Ebola virus in the semen of survivors over time.

Until such time as their semen has twice tested negative for Ebola, survivors should practise good hand and personal hygiene by immediately and thoroughly washing with soap and water after any physical contact with semen, including after masturbation. During this period

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used condoms should be handled safely, and safely disposed of, so as to prevent contact with seminal fluids.

All survivors, their partners and families should be shown respect, dignity and compassion. Read the interim advice on the sexual transmission of the Ebola virus disease

Symptoms of Ebola virus disease

The incubation period, that is, the time interval from infection with the virus to onset of symptoms is 2 to 21 days. Humans are not infectious until they develop symptoms. First symptoms are the sudden onset of fever fatigue, muscle pain, headache and sore throat. This is followed by vomiting, diarrhoea, rash, symptoms of impaired kidney and liver function, and in some cases, both internal and external bleeding (e.g. oozing from the gums, blood in the stools). Laboratory findings include low white blood cell and platelet counts and elevated liver enzymes.


It can be difficult to distinguish EVD from other infectious diseases such as malaria, typhoid fever and meningitis. Confirmation that symptoms are caused by Ebola virus infection are made using the following investigations:

antibody-capture enzyme-linked immunosorbent assay (ELISA) antigen-capture detection tests serum neutralization test reverse transcriptase polymerase chain reaction (RT-PCR) assay electron microscopy virus isolation by cell culture. Samples from patients are an extreme biohazard risk; laboratory testing on non-inactivated

samples should be conducted under maximum biological containment conditions.

Treatment and vaccines

Supportive care-rehydration with oral or intravenous fluids- and treatment of specific symptoms, improves survival. There is as yet no proven treatment available for EVD. However, a range of potential treatments including blood products, immune therapies and drug therapies are currently being evaluated. No licensed vaccines are available yet, but 2 potential vaccines are undergoing human safety testing.Prevention and control

Good outbreak control relies on applying a package of interventions, namely case management, surveillance and contact tracing, a good laboratory service, safe burials and social mobilisation. Community engagement is key to successfully controlling outbreaks. Raising awareness of risk factors for Ebola infection and protective measures that individuals can take is an effective way to reduce human transmission. Risk reduction messaging should focus on several factors:

Reducing the risk of wildlife-to-human transmission from contact with infected fruit bats or monkeys/apes and the consumption of their raw meat. Animals should be handled with gloves and other appropriate protective clothing. Animal products (blood and meat) should be thoroughly cooked before consumption.

Reducing the risk of human-to-human transmission from direct or close contact with people with Ebola symptoms, particularly with their bodily fluids. Gloves and appropriate personal protective equipment should be worn when taking care of ill patients at home. Regular hand

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washing is required after visiting patients in hospital, as well as after taking care of patients at home.

Reducing the risk of possible sexual transmission, because the risk of sexual transmission cannot be ruled out, men and women who have recovered from Ebola should abstain from all types of sex (including anal- and oral sex) for at least three months after onset of symptoms. If sexual abstinence is not possible, male or female condom use is recommended. Contact with body fluids should be avoided and washing with soap and water is recommended. WHO does not recommend isolation of male or female convalescent patients whose blood has been tested negative for Ebola virus.

Outbreak containment measures, including prompt and safe burial of the dead, identifying people who may have been in contact with someone infected with Ebola and monitoring their health for 21 days, the importance of separating the healthy from the sick to prevent further spread, and the importance of good hygiene and maintaining a clean environment.

Controlling infection in health-care settings:

Health-care workers should always take standard precautions when caring for patients, regardless of their presumed diagnosis. These include basic hand hygiene, respiratory hygiene, use of personal protective equipment (to block splashes or other contact with infected materials), safe injection practices and safe burial practices.Health-care workers caring for patients with suspected or confirmed Ebola virus should apply extra infection control measures to prevent contact with the patient’s blood and body fluids and contaminated surfaces or materials such as clothing and bedding. When in close contact (within 1 metre) of patients with EBV, health-care workers should wear face protection (a face shield or a medical mask and goggles), a clean, non-sterile long-sleeved gown, and gloves (sterile gloves for some procedures).Laboratory workers are also at risk. Samples taken from humans and animals for investigation of Ebola infection should be handled by trained staff and processed in suitably equipped laboratories.

WHO responseWHO aims to prevent Ebola outbreaks by maintaining surveillance for Ebola virus disease and supporting at-risk countries to developed preparedness plans. The document provides overall guidance for control of Ebola and Marburg virus outbreaks:

Ebola and Marburg virus disease epidemics: preparedness, alert, control, and evaluation When an outbreak is detected WHO responds by supporting surveillance, community

engagement, case management, laboratory services, contact tracing, infection control, logistical support and training and assistance with safe burial practices.

WHO has developed detailed advice on Ebola infection prevention and control: Infection prevention and control guidance for care of patients with suspected or confirmed

Filovirus haemorrhagic fever in health-care settings, with focus on Ebola

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Hepatitis A

Fact sheet N°328Updated July 2015

Key facts

Hepatitis A is a viral liver disease that can cause mild to severe illness. The hepatitis A virus is transmitted through ingestion of contaminated food and water or

through direct contact with an infectious person. Almost everyone recovers fully from hepatitis A, but very small proportions die from

fulminant hepatitis. Hepatitis A infection risk is associated with a lack of safe water and poor sanitation. Epidemics can be explosive and cause significant economic loss. Improved sanitation and the hepatitis A vaccine are the most effective ways to combat the


Hepatitis A is a liver disease caused by the hepatitis A virus. The virus is primarily spread when an uninfected (and unvaccinated) person ingests food or water that is contaminated with the faeces of an infected person. The disease is closely associated with unsafe water, inadequate sanitation and poor personal hygiene.Unlike hepatitis B and C, hepatitis A infection does not cause chronic liver disease and is rarely fatal, but it can cause debilitating symptoms and fulminant hepatitis (acute liver failure), which is associated with high mortality.Hepatitis A occurs sporadically and in epidemics worldwide, with a tendency for cyclic recurrences. The hepatitis A virus is one of the most frequent causes of foodborne infection. Epidemics related to contaminated food or water can erupt explosively, such as the epidemic in Shanghai in 1988 that affected about 300 000 people1. Hepatitis A viruses persist in the environment and can withstand food-production processes routinely used to inactivate and/or control bacterial pathogens.The disease can lead to significant economic and social consequences in communities. It can take weeks or months for people recovering from the illness to return to work, school or daily life. The impact on food establishments identified with the virus, and local productivity in general, can be substantial.

Geographical distribution

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Geographical distribution areas can be characterized as having high, intermediate or low levels of hepatitis A infection.

Areas with high levels of infectionIn developing countries with very poor sanitary conditions and hygienic practices, most children (90%) have been infected with the hepatitis A virus before the age of 10 years2. Those infected in childhood do not experience any noticeable symptoms. Epidemics are uncommon because older children and adults are generally immune. Symptomatic disease rates in these areas are low and outbreaks are rare.

Areas with intermediate levels of infectionIn developing countries, countries with transitional economies and regions where sanitary conditions are variable, children often escape infection in early childhood. Ironically, these improved economic and sanitary conditions may lead to a higher susceptibility in older age groups and higher disease rates, as infections occur in adolescents and adults, and large outbreaks can occur.

Areas with low levels of infectionIn developed countries with good sanitary and hygienic conditions, infection rates are low. Disease may occur among adolescents and adults in high-risk groups, such as injecting-drug users, men who have sex with men, people travelling to areas of high endemicity, and in isolated populations, such as closed religious communities.


The hepatitis A virus is transmitted primarily by the faecal-oral route; that is when an uninfected person ingests food or water that has been contaminated with the faeces of an infected person. Waterborne outbreaks, though infrequent, are usually associated with sewage-contaminated or inadequately treated water.The virus can also be transmitted through close physical contact with an infectious person, although casual contact among people does not spread the virus.


The incubation period of hepatitis A is usually 14–28 days.Symptoms of hepatitis A range from mild to severe, and can include fever, malaise, loss of appetite, diarrhoea, nausea, abdominal discomfort, dark-coloured urine and jaundice (a yellowing of the skin and whites of the eyes). Not everyone who is infected will have all of the symptoms.Adults have signs and symptoms of illness more often than children, and the severity of disease and mortality increases in older age groups. Infected children under 6 years of age do not usually experience noticeable symptoms, and only 10% develop jaundice. Among older children and adults, infection usually causes more severe symptoms, with jaundice occurring in more than 70% of cases.

Who is at risk?

Anyone who has not been vaccinated or previously infected can contract hepatitis A. In areas where the virus is widespread (high endemicity), most hepatitis A infections occur during early childhood. Risk factors include:

poor sanitation;

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lack of safe water; injecting drugs; living in a household with an infected person; being a sexual partner of someone with acute hepatitis A infection; and travelling to areas of high endemicity without being immunized.


Cases of hepatitis A are not clinically distinguishable from other types of acute viral hepatitis. Specific diagnosis is made by the detection of HAV-specific IgM and IgG antibodies in the blood. Additional tests include reverse transcriptase polymerase chain reaction (RT-PCR) to detect the hepatitis A virus RNA, but may require specialised laboratory facilities.Treatment

There is no specific treatment for hepatitis A. Recovery from symptoms following infection may be slow and may take several weeks or months. Therapy is aimed at maintaining comfort and adequate nutritional balance, including replacement of fluids that are lost from vomiting and diarrhoea.Prevention

Improved sanitation, food safety and immunization are the most effective ways to combat hepatitis A.The spread of hepatitis A can be reduced by:

adequate supplies of safe drinking water; proper disposal of sewage within communities; and personal hygiene practices such as regular hand-washing with safe water. Several hepatitis A vaccines are available internationally. All are similar in terms of how well

they protect people from the virus and their side-effects. No vaccine is licensed for children younger than 1 year of age.

Nearly 100% of people develop protective levels of antibodies to the virus within 1 month after a single dose of the vaccine. Even after exposure to the virus, a single dose of the vaccine within 2 weeks of contact with the virus has protective effects. Still, manufacturers recommend two vaccine doses to ensure a longer-term protection of about 5 to 8 years after vaccination.

Millions of people have been immunized worldwide with no serious adverse events. The vaccine can be given as part of regular childhood immunizations programmes and also with other vaccines for travellers.

Immunization efforts

Vaccination against hepatitis A should be part of a comprehensive plan for the prevention and control of viral hepatitis. Planning for large-scale immunization programmes should involve careful economic evaluations and consider alternative or additional prevention methods, such as improved sanitation, and health education for improved hygiene practices.Whether or not to include the vaccine in routine childhood immunizations depends on the local context. The proportion of susceptible people in the population and the level of exposure to the virus should be considered. Several countries, including Argentina, China, Israel, Turkey, and the United States of America have introduced the vaccine in routine childhood immunizations.While the 2 dose regimen of inactivated hepatitis A vaccine is used in many countries, other countries may consider inclusion of a single-dose inactivated hepatitis A vaccine in their

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immunization schedules. Some countries also recommend the vaccine for people at increased risk of hepatitis A, including:

travellers to countries where the virus is endemic; men who have sex with men; and people with chronic liver disease (because of their increased risk of serious complications if

they acquire hepatitis A infection). Regarding immunization for outbreak response, recommendations for hepatitis A vaccination

should also be site-specific. The feasibility of rapidly implementing a widespread immunization campaign needs to be included.

Vaccination to control community-wide outbreaks is most successful in small communities, when the campaign is started early and when high coverage of multiple age groups is achieved. Vaccination efforts should be supplemented by health education to improve sanitation, hygiene practices and food safety.

WHO response

WHO is working in the following areas to prevent and control viral hepatitis: raising awareness, promoting partnerships and mobilizing resources; formulating evidence-based policy and data for action; preventing transmission; and executing screening, care and treatment. WHO also organizes World Hepatitis Day on July 28 every year to increase awareness and

understanding of viral hepatitis.

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Hepatitis B

Fact sheet N°204 Updated July 2015

Key facts

Hepatitis B is a viral infection that attacks the liver and can cause both acute and chronic disease.

The virus is transmitted through contact with the blood or other body fluids of an infected person.

An estimated 240 million people are chronically infected with hepatitis B (defined as hepatitis B surface antigen positive for at least 6 months).

More than 780 000 people die every year due to complications of hepatitis B, including cirrhosis and liver cancer1.

Hepatitis B is an important occupational hazard for health workers. However, it can be prevented by currently available safe and effective vaccine.

Hepatitis B is a potentially life-threatening liver infection caused by the hepatitis B virus. It is a major global health problem. It can cause chronic infection and puts people at high risk of death from cirrhosis and liver cancer.A vaccine against hepatitis B has been available since 1982. The vaccine is 95% effective in preventing infection and the development of chronic disease and liver cancer due to hepatitis B.

Geographical distribution

Hepatitis B prevalence is highest in sub-Saharan Africa and East Asia, where between 5–10% of the adult population is chronically infected. High rates of chronic infections are also found in the Amazon and the southern parts of eastern and central Europe. In the Middle East and the Indian subcontinent, an estimated 2–5% of the general population is chronically infected. Less than 1% of the population in Western Europe and North America is chronically infected.


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The hepatitis B virus can survive outside the body for at least 7 days. During this time, the virus can still cause infection if it enters the body of a person who is not protected by the vaccine. The incubation period of the hepatitis B virus is 75 days on average, but can vary from 30 to 180 days. The virus may be detected within 30 to 60 days after infection and can persist and develop into chronic hepatitis B.In highly endemic areas, hepatitis B is most commonly spread from mother to child at birth (perinatal transmission), or through horizontal transmission (exposure to infected blood), especially from an infected child to an uninfected child during the first 5 years of life. The development of chronic infection is very common in infants infected from their mothers or before the age of 5 years.Hepatitis B is also spread by percutaneous or mucosal exposure to infected blood and various body fluids, as well as through saliva, menstrual, vaginal, and seminal fluids. Sexual transmission of hepatitis B may occur, particularly in unvaccinated men who have sex with men and heterosexual persons with multiple sex partners or contact with sex workers. Infection in adulthood leads to chronic hepatitis in less than 5% of cases. Transmission of the virus may also occur through the reuse of needles and syringes either in health-care settings or among persons who inject drugs. In addition, infection can occur during medical, surgical and dental procedures, tattooing, or through the use of razors and similar objects that are contaminated with infected blood.


Most people do not experience any symptoms during the acute infection phase. However, some people have acute illness with symptoms that last several weeks, including yellowing of the skin and eyes (jaundice), dark urine, extreme fatigue, nausea, vomiting and abdominal pain. A small subset of persons with acute hepatitis can develop acute liver failure which can lead to death.In some people, the hepatitis B virus can also cause a chronic liver infection that can later develop into cirrhosis of the liver or liver cancer.More than 90% of healthy adults who are infected with the hepatitis B virus will recover naturally from the virus within the first year.

Who is at risk for chronic disease?

The likelihood that infection with the virus becomes chronic depends upon the age at which a person becomes infected. Children less than 6 years of age who become infected with the hepatitis B virus are the most likely to develop chronic infections.In infants and children:

80–90% of infants infected during the first year of life develop chronic infections; 30–50% of children infected before the age of 6 years develop chronic infections. In adults: <5% of otherwise healthy persons who are infected as adults will develop chronic infection; 20–30% of adults who are chronically infected will develop cirrhosis and/or liver cancer.


It is not possible, on clinical grounds, to differentiate hepatitis B from hepatitis caused by other viral agents and, hence, laboratory confirmation of the diagnosis is essential. A number of blood tests are available to diagnose and monitor people with hepatitis B. They can be used to distinguish acute and chronic infections.Laboratory diagnosis of hepatitis B infection focuses on the detection of the hepatitis B surface antigen HBsAg. WHO recommends that all blood donations are tested for hepatitis B to ensure blood safety and avoid accidental transmission to people who receive blood products.

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Acute HBV infection is characterized by the presence of HBsAg and immunoglobulin M (IgM) antibody to the core antigen, HBcAg. During the initial phase of infection, patients are also seropositive for hepatitis B e antigen (HBeAg). HBeAg is usually a marker of high levels of replication of the virus. The presence of HBeAg indicates that the blood and body fluids of the infected individual are highly contagious.

Chronic infection is characterized by the persistence of HBsAg for at least 6 months (with or without concurrent HBeAg). Persistence of HBsAg is the principal marker of risk for developing chronic liver disease and liver cancer (hepatocellular carcinoma) later in life.


There is no specific treatment for acute hepatitis B. Therefore, care is aimed at maintaining comfort and adequate nutritional balance, including replacement of fluids lost from vomiting and diarrhoea. Chronic hepatitis B infection can be treated with drugs, including oral antiviral agents. Treatment can slow the progression of cirrhosis, reduce incidence of liver cancer and improve long term survival.WHO recommends the use of oral treatments - tenofovir or entecavir, because these are the most potent drugs to suppress hepatitis B virus. They rarely lead to drug resistance as compared with other drugs, are simple to take (1 pill a day), and have few side effects so require only limited monitoring.However, in most people, the treatment does not cure hepatitis B infection, but only suppresses the replication of the virus. Therefore, most people who start hepatitis B treatment must continue it for life.Treatment using interferon injections may be considered in some people in certain high-income settings, but its use is less feasible in low-resource settings due to high cost and significant adverse effects requiring careful monitoring.There is still limited access to diagnosis and treatment of hepatitis B in many resource-constrained settings, and many people are diagnosed only when they already have advanced liver disease. Liver cancer progresses rapidly, and since treatment options are limited, the outcome is in general poor. In low-income settings, most people with liver cancer die within months of diagnosis. In high-income countries, surgery and chemotherapy can prolong life for up to a few years. In high-income countries, liver transplantation is sometimes used in people with cirrhosis, with varying success.


The hepatitis B vaccine is the mainstay of hepatitis B prevention. WHO recommends that all infants receive the hepatitis B vaccine as soon as possible after birth, preferably within 24 hours. The birth dose should be followed by 2 or 3 doses to complete the primary series. In most cases, one of the following two options is considered appropriate:

a 3-dose schedule of hepatitis B vaccine, with the first dose (monovalent) being given at birth and the second and third (monovalent or combined vaccine) given at the same time as the first and third doses of diphtheria, pertussis (whooping cough), and tetanus – (DTP) vaccine; or

4 doses, where a monovalent birth dose is followed by three monovalent or combined vaccine doses, usually given with other routine infant vaccines.

The complete vaccine series induces protective antibody levels in more than 95% of infants, children and young adults. Protection lasts at least 20 years and is probably lifelong. Thus, WHO does not recommend booster vaccination for persons who have completed the 3 dose vaccination schedule.

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All children and adolescents younger than 18 years-old and not previously vaccinated should receive the vaccine if they live in countries where there is low or intermediate endemicity. In those settings it is possible that more people in high-risk groups may acquire the infection and they should also be vaccinated. They include:

people who frequently require blood or blood products, dialysis patients, recipients of solid organ transplantations;

people interned in prisons; persons who inject drugs; household and sexual contacts of people with chronic HBV infection; people with multiple sexual partners; health-care workers and others who may be exposed to blood and blood products through

their work; and travellers who have not completed their hepatitis B vaccination series, who should be

offered the vaccine before leaving for endemic areas. The vaccine has an excellent record of safety and effectiveness. Since 1982, over 1 billion

doses of hepatitis B vaccine have been used worldwide. In many countries where 8–15% of children used to become chronically infected with the hepatitis B virus, vaccination has reduced the rate of chronic infection to less than 1% among immunized children.

As of 2013, 183 Member States vaccinate infants against hepatitis B as part of their vaccination schedules and 81% of children received the hepatitis B vaccine. This is a major increase compared with 31 countries in 1992, the year that the World Health Assembly passed a resolution to recommend global vaccination against hepatitis B. Furthermore, as of 2013, 93 Member States have introduced the hepatitis B birth dose vaccine.In addition, implementing of blood safety strategies, including quality-assured screening of all donated blood and blood components used for transfusion, can prevent transmission of HBV. Safe injection practices, eliminating unnecessary and unsafe injections, can be effective strategies to protect against HBV transmission. Furthermore, safer sex practices, including minimizing the number of partners and using barrier protective measures (condoms), also protect against transmission.

WHO response

In March 2015, WHO launched its first "Guidelines for the prevention, care and treatment of persons living with chronic hepatitis B infection". The recommendations:

promote the use of simple, non-invasive diagnostic tests to assess the stage of liver disease and eligibility for treatment;

prioritize treatment for those with most advanced liver disease and at greatest risk of mortality; and

recommend the preferred use of the nucleos(t)ide analogues with a high barrier to drug resistance (tenofovir and entecavir, and entecavir in children aged 2–11 years) for first- and second-line treatment.

These guidelines also recommend lifelong treatment in those with cirrhosis; and regular monitoring for disease progression, toxicity of drugs and early detection of liver cancer.

WHO is working in the following areas to prevent and control viral hepatitis: raising awareness, promoting partnerships; formulating evidence-based policy and data for action; promoting prevention of transmission through vaccination, safe injection practices and blood

safety; and

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promoting wider access to monitoring and screening, care and treatment services for hepatitis B.

WHO also organizes World Hepatitis Day on July 28 every year to increase awareness and understanding of viral hepatitis.


Fact sheet N°360Updated July 2015

Key facts

HIV continues to be a major global public health issue, having claimed more than 34 million lives so far. In 2014, 1.2 [1.0–1.5] million people died from HIV-related causes globally.

There were approximately 36.9 [34.3–41.4] million people living with HIV at the end of 2014 with 2.0 [1.9–2.2] million people becoming newly infected with HIV in 2014 globally.

Sub-Saharan Africa is the most affected region, with 25.8 [24.0–28.7] million people living with HIV in 2014. Also sub-Saharan Africa accounts for almost 70% of the global total of new HIV infections.

HIV infection is often diagnosed through rapid diagnostic tests (RDTs), which detect the presence or absence of HIV antibodies. Most often these tests provide same day test results; essential for same day diagnosis and early treatment and care.

There is no cure for HIV infection. However, effective treatment with antiretroviral (ARV) drugs can control the virus so that people with HIV can enjoy healthy and productive lives.

It is estimated that currently only 51% of people with HIV know their status. In 2014, approximately 150 million children and adults in 129 low- and middle-income countries received HIV testing services.

In 2014, 14.9 million people living with HIV were receiving antiretroviral therapy (ART) globally, of which 13.5 million were receiving ART in low- and middle-income countries. The 14.9 million people on ART represent 40% [37–45%] of people living with HIV globally

The Human Immunodeficiency Virus (HIV) targets the immune system and weakens people's defence systems against infections and some types of cancer. As the virus destroys and impairs the function of immune cells, infected individuals gradually become immunodeficient. Immune function is typically measured by CD4 cell count. Immunodeficiency results in increased susceptibility to a wide range of infections and diseases that people with healthy immune systems can fight off.

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The most advanced stage of HIV infection is Acquired Immunodeficiency Syndrome (AIDS), which can take from 2 to 15 years to develop depending on the individual. AIDS is defined by the development of certain cancers, infections, or other severe clinical manifestations.

Signs and symptoms

The symptoms of HIV vary depending on the stage of infection. Though people living with HIV tend to be most infectious in the first few months, many are unaware of their status until later stages. The first few weeks after initial infection, individuals may experience no symptoms or an influenza-like illness including fever, headache, rash or sore throat.As the infection progressively weakens the immune system, an individual can develop other signs and symptoms, such as swollen lymph nodes, weight loss, fever, diarrhoea and cough. Without treatment, they could also develop severe illnesses such as tuberculosis, cryptococcal meningitis, and cancers such as lymphomas and Kaposi's sarcoma, among others.


HIV can be transmitted via the exchange of a variety of body fluids from infected individuals, such as blood, breast milk, semen and vaginal secretions. Individuals cannot become infected through ordinary day-to-day contact such as kissing, hugging, shaking hands, or sharing personal objects, food or water.

Risk factors

Behaviours and conditions that put individuals at greater risk of contracting HIV include: having unprotected anal or vaginal sex; having another sexually transmitted infection such as syphilis, herpes, chlamydia,

gonorrhoea, and bacterial vaginosis; sharing contaminated needles, syringes and other injecting equipment and drug solutions

when injecting drugs; receiving unsafe injections, blood transfusions, medical procedures that involve unsterile

cutting or piercing; and experiencing accidental needle stick injuries, including among health workers.


Serological tests, such as RDTs or enzyme immunoassays (EIAs), detect the presence or absence of antibodies to HIV-1/2 and/or HIV p24 antigen. When such tests are used within a testing strategy according to a validated testing algorithm, HIV infection can be detected with great accuracy. It is important to note that serological tests detect antibodies produced by an individual as part of their immune system to fight off foreign pathogens, rather than direct detection of HIV itself.Most individuals develop antibodies to HIV-1/2 within 28 days and therefore antibodies may not be detectable early after infection, the so-called window period. This early period of infection represents the time of greatest infectivity; however HIV transmission can occur during all stages of the infection.It is best practice to also retest all people initially diagnosed as HIV-positive before they enroll in care and/or treatment to rule out any potential testing or reporting error.

HIV testing services

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HIV testing should be voluntary and the right to decline testing should be recognized. Mandatory or coerced testing by a health-care provider, authority or by a partner or family member is not acceptable as it undermines good public health practice and infringes on human rights.Some countries have introduced, or are considering, self-testing as an additional option. HIV self-testing is a process whereby a person who wants to know his or her HIV status collects a specimen, performs a test and interprets the test results in private. HIV self-testing does not provide a definitive diagnosis; instead, it is an initial test which requires further testing by a health worker using a national validated testing algorithm.All HIV testing services must include the 5 C’s recommended by WHO: informed Consent, Confidentiality, Counselling, Correct test results and Connection (linkage to care, treatment and other services).


Individuals can reduce the risk of HIV infection by limiting exposure to risk factors. Key approaches for HIV prevention, which are often used in combination, include:

1. Male and female condom use

Correct and consistent use of male and female condoms during vaginal or anal penetration can protect against the spread of sexually transmitted infections, including HIV. Evidence shows that male latex condoms have an 85% or greater protective effect against HIV and other sexually transmitted infections (STIs).

2. Testing and counselling for HIV and STIs

Testing for HIV and other STIs is strongly advised for all people exposed to any of the risk factors. This way people learn of their own infection status and access necessary prevention and treatment services without delay. WHO also recommends offering testing for partners or couples.Tuberculosis (TB) is the most common presenting illness among people with HIV. It is fatal if undetected or untreated and is the leading cause of death among people with HIV- responsible for roughly 1 of every 4 HIV-associated deaths. Early detection of TB and prompt linkage to TB treatment and ART can prevent these deaths. It is strongly advised that HIV testing services integrate screening for TB and that all individuals diagnosed with HIV and active TB urgently use ART.

3. Voluntary medical male circumcision

Medical male circumcision, when safely provided by well-trained health professionals, reduces the risk of heterosexually acquired HIV infection in men by approximately 60%. This is a key intervention in generalized epidemic settings with high HIV prevalence and low male circumcision rates.

4. Antiretroviral (ART) use for prevention

4.1 ART as preventionA 2011 trial has confirmed if an HIV-positive person adheres to an effective ART regimen, the risk of transmitting the virus to their uninfected sexual partner can be reduced by 96%. For couples in which

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one partner is HIV-positive and the other HIV-negative, WHO recommend offering ART for the HIV-positive partner regardless of her/his CD4 count.

4.2 Pre-exposure prophylaxis (PrEP) for HIV-negative partnerOral PrEP of HIV is the daily use of ARV drugs by HIV-uninfected people to block the acquisition of HIV. More than 10 randomized controlled studies have demonstrated the effectiveness of PrEP in reducing HIV transmission among a range of populations including serodiscordant heterosexual couples (where one partner is infected and the other is not), men who have sex with men, transgender women, high-risk heterosexual couples, and people who inject drugs.In July 2014, WHO released "Consolidated guidelines on HIV prevention, diagnosis, treatment and care for key populations" which recommended PrEP as an additional HIV prevention choice within a comprehensive HIV prevention package for men who have sex with men.

4.3 Post-exposure prophylaxis for HIV (PEP)Post-exposure prophylaxis (PEP) is the use of ARV drugs within 72 hours of exposure to HIV in order to prevent infection. PEP includes counselling, first aid care, HIV testing, and administering of a 28-day course of ARV drugs with follow-up care.Updated WHO guidelines issued in December 2014 recommend PEP use for both occupational and non-occupational exposures and for adults and children. The new recommendations provide simpler regimens using ARVs already being used in treatment. The implementation of the new guidelines will enable easier prescribing, better adherence and increased completion rates of PEP to prevent HIV in people who have been accidentally exposed to HIV such as health workers or through unprotected sexual exposures or sexual assault.

5. Harm reduction for injecting drug users

People who inject drugs can take precautions against becoming infected with HIV by using sterile injecting equipment, including needles and syringes, for each injection. A comprehensive package of interventions for HIV prevention and treatment includes:

needle and syringe programmes; opioid substitution therapy for people dependent on opioids and other evidence based drug

dependence treatment; HIV testing and counselling; HIV treatment and care; access to condoms; and management of STIs, tuberculosis and viral hepatitis.

6. Elimination of mother-to-child transmission of HIV (eMTCT)

The transmission of HIV from an HIV-positive mother to her child during pregnancy, labour, delivery or breastfeeding is called vertical or mother-to-child transmission (MTCT). In the absence of any interventions during these stages, rates of HIV transmission from mother-to-child can be between 15-45%. MTCT can be nearly fully prevented if both the mother and the child are provided with ARV drugs throughout the stages when infection could occur.WHO recommends options for prevention of MTCT (PMTCT), which includes providing ARVs to mothers and infants during pregnancy, labour and the post-natal period, and offering life-long treatment to HIV-positive pregnant women regardless of their CD4 count.In 2014, 73% [68–79%] of the estimated 1.5 [1.3-1.6] million pregnant women living with HIV globally received effective antiretroviral drugs to avoid transmission to their children.

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HIV can be suppressed by combination ART consisting of 3 or more ARV drugs. ART does not cure HIV infection but controls viral replication within a person's body and allows an individual's immune system to strengthen and regain the capacity to fight off infections.Approximately 14.9 million people living with HIV were receiving ART at the end of 2014 globally. About 823 000 of those were children.In 2014, there was a large increase in number of people on ART –1.9 million-- in a single year.WHO recommends initiating ART when their CD4 cell counts falls to 500 cells/mm³ or less. ART regardless of CD4 count is recommended for all people living with HIV in serodiscordant couples, pregnant and breastfeeding women living with HIV, people with TB and HIV, and people co-infected with HIV and hepatitis B infection with severe chronic liver disease. Likewise, ART is recommended for all children living with HIV who are younger than 5 years-old.

WHO response

WHO is working with countries to implement the Global Health Sector Strategy on HIV/AIDS for 2011-2015. WHO has identified six operational objectives for 2014–2015 to support countries most efficiently in moving towards the global HIV targets. These are to support:

strategic use of ARVs for HIV treatment and prevention; eliminating HIV in children and expanding access to paediatric treatment; an improved health sector response to HIV among key populations; further innovation in HIV prevention, diagnosis, treatment and care; strategic information for effective scale up; stronger links between HIV and related health outcomes.

WHO is a cosponsor of the Joint United Nations Programme on AIDS (UNAIDS). Within UNAIDS, WHO leads activities on HIV treatment and care, HIV and tuberculosis co-infection, and jointly coordinates with UNICEF the work on the elimination of mother-to-child transmission of HIV.Currently, WHO is working on a follow-up strategy for the global health sector response to HIV for 2016-2021.

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Influenza (Seasonal)

Fact sheet N°211March 2014

Key facts

Seasonal influenza is an acute viral infection that spreads easily from person to person. Seasonal influenza viruses circulate worldwide and can affect anybody in any age group. Seasonal influenza viruses cause annual epidemics that peak during winter in temperate

regions. Seasonal influenza is a serious public health problem that causes severe illness and death in

high risk populations. An influenza epidemic can take an economic toll through lost workforce productivity and

strain health services. Influenza vaccination is the most effective way to prevent infection. Antiviral drugs are available for treatment, however influenza viruses can develop resistance

to the drugs.


Seasonal influenza is an acute viral infection caused by an influenza virus.There are 3 types of seasonal influenza viruses – A, B and C. Type A influenza viruses are further classified into subtypes according to the combinations of various virus surface proteins. Among many subtypes of influenza A viruses, influenza A(H1N1) and A(H3N2) subtypes are currently circulating among humans.Influenza viruses circulate in all parts of the world. Type C influenza cases occur much less frequently than A and B. That is why only influenza A and B viruses are included in seasonal influenza vaccines.

Signs and symptoms

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Seasonal influenza is characterized by a sudden onset of high fever, cough (usually dry), headache, muscle and joint pain, severe malaise (feeling unwell), sore throat and runny nose. Cough can be severe and can last 2 or more weeks. Most people recover from fever and other symptoms within a week without requiring medical attention. But influenza can cause severe illness or death especially in people at high risk (see below). The time from infection to illness, known as the incubation period, is about 2 days.

Who is at risk?

Yearly influenza epidemics can seriously affect all populations, but the highest risk of complications occur among children younger than age 2 years, adults aged 65 years or older, pregnant women, and people of any age with certain medical conditions, such as chronic heart, lung, kidney, liver, blood or metabolic diseases (such as diabetes), or weakened immune systems.


Seasonal influenza spreads easily and can sweep through schools, nursing homes, businesses or towns. When an infected person coughs, infected droplets get into the air and another person can breathe them in and be exposed. The virus can also be spread by hands contaminated with influenza viruses. To prevent transmission, people should cover their mouth and nose with a tissue when coughing, and wash their hands regularly.

Seasonal epidemics and disease burden

In temperate climates, seasonal epidemics occur mainly during winter while in tropical regions, influenza may occur throughout the year, causing outbreaks more irregularly.Influenza occurs globally with an annual attack rate estimated at 5%–10% in adults and 20%–30% in children. Illnesses can result in hospitalization and death mainly among high-risk groups (the very young, elderly or chronically ill). Worldwide, these annual epidemics are estimated to result in about 3 to 5 million cases of severe illness, and about 250 000 to 500 000 deaths.In industrialized countries most deaths associated with influenza occur among people age 65 or older. Epidemics can result in high levels of worker/school absenteeism and productivity losses. Clinics and hospitals can be overwhelmed during peak illness periods.The precise effects of seasonal influenza epidemics in developing countries are not known, but research estimates indicate that a large percent of child deaths associated with influenza occur in developing countries every year.


The most effective way to prevent the disease and/or severe outcomes from the illness is vaccination. Safe and effective vaccines are available and have been used for more than 60 years. Among healthy adults, influenza vaccine can provide reasonable protection. However among the elderly, influenza vaccine may be less effective in preventing illness but may reduce severity of disease and incidence of complications and deaths.Vaccination is especially important for people at higher risk of serious influenza complications, and for people who live with or care for high risk individuals.WHO recommends annual vaccination for:

pregnant women at any stage of pregnancy children aged 6 months to 5 years elderly individuals (≥65 years of age)

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individuals with chronic medical conditions health-care workers.

Influenza vaccination is most effective when circulating viruses are well-matched with vaccine viruses. Influenza viruses are constantly changing, and the WHO Global Influenza Surveillance and Response System (GISRS) – a partnership of National Influenza Centres around the world –monitors the influenza viruses circulating in humans.For many years WHO has updated its recommendation on vaccine composition biannually that targets the 3 (trivalent) most representative virus types in circulation (two subtypes of influenza A viruses and one B virus). Starting with the 2013-2014 northern hemisphere influenza season, quadrivalent vaccine composition has been recommended with a second influenza B virus in addition to the viruses in the conventional trivalent vaccines. Quadrivalent influenza vaccines are expected to provide wider protection against influenza B virus infections.


Antiviral drugs for influenza are available in some countries and may reduce severe complications and deaths. Ideally they need to be administered early (within 48 hours of onset of symptoms) in the disease. There are 2 classes of such medicines:1. adamantanes1(amantadine and rimantadine); and2. inhibitors of influenza neuraminidase (oseltamivir and zanamivir; as well as peramivir and

laninamivir licensed in several countries).Some influenza viruses develop resistance to the antiviral medicines, limiting the effectiveness of treatment. WHO monitors antiviral susceptibility among circulating influenza viruses to provide timely guidance for antiviral use in clinical management and potential chemoprophylaxis.

WHO response

WHO, with its partners, monitors influenza globally, recommends seasonal influenza vaccine compositions twice a year for the Northern and Southern hemispheres, and supports Member States efforts to develop prevention and control strategies.WHO works to strengthen national and regional influenza diagnostic capacities including antiviral susceptibility monitoring, disease surveillance, outbreak responses, and increase vaccine coverage among high-risk groups.

1Currently, WHO recommends neuraminidase inhibitors as the first-line treatment for people requiring antiviral therapy, as the currently circulating influenza viruses are resistant to the adamantanes.

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Fact sheet N°101 Updated May 2015

Key facts

Leprosy is a chronic disease caused by a slow multiplying bacillus,Mycobacterium leprae. M. leprae multiplies slowly and the incubation period of the disease is about 5 years.

Symptoms can take as long as 20 years to appear. The disease mainly affects the skin, the peripheral nerves, mucosa of the upper respiratory

tract and also the eyes. Leprosy is curable. Although not highly infectious, it is transmitted via droplets, from the nose and mouth,

during close and frequent contacts with untreated cases. Early diagnosis and treatment with multidrug therapy (MDT) remain key in eliminating the

disease as a public health concern Untreated, leprosy can cause progressive and permanent damage to the skin, nerves, limbs

and eyes. Official figures from 103 countries from 5 WHO regions show the global registered

prevalence of leprosy to be at 180 618 at the end of 2013; during the same year, 215 656 new cases were reported.

Leprosy is a chronic infectious disease caused by Mycobacterium leprae, an acid-fast, rod-shaped bacillus. The disease mainly affects the skin, the peripheral nerves, mucosa of the upper respiratory tract and also the eyes.Leprosy is curable and treatment provided in the early stages averts disability.

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Multidrug therapy (MDT) treatment has been made available by WHO free of charge to all patients worldwide since 1995, and provides a simple yet highly effective cure for all types of leprosy.Elimination of leprosy globally was achieved in the year 2000 (i.e. a prevalence rate of leprosy less than 1 case per 10 000 persons at the global level). Nearly 16 million leprosy patients have been cured with MDT over the past 20 years.

Leprosy today

Leprosy control has improved significantly due to national and subnational campaigns in most endemic countries. Integration of primary leprosy services into existing general health services has made diagnosis and treatment of the disease easy.Detection of all cases in a community and completion of prescribed treatment using MDT are the basic tenets of the Enhanced Global Strategy for Further Reducing Disease Burden Due to Leprosy (plan period: 2011–2015).The Strategy emphasizes the need to sustain expertise and increase the number of skilled leprosy staff, improve the participation of affected persons in leprosy services and reduce visible deformities – otherwise called Grade 2 disabilities (G2D cases) – as well as stigma associated with the disease.National leprosy programmes for 2011–2015 now focus more on underserved populations and inaccessible areas to improve access and coverage. Since control strategies are limited, national programmes actively improve case-holding, contact tracing, monitoring, referrals and record management.According to official reports received from 103 countries from 5 WHO regions, the global registered prevalence of leprosy at the end of 2013 was 180 618 cases. The number of new cases reported globally in 2013 was 215 656 compared with 232 857 in 2012 and 226 626 in 2011.The number of new cases indicates the degree of continued transmission of infection in the community. A total of 13 countries reported zero cases in 2013. Global statistics show that 206 107 (96%) of new leprosy cases were reported from 14 countries and only 4% of new cases from the rest of the world. Only these 14 countries reported >1000 new cases in 2013.Pockets of high endemicity still remain in some areas of many countries but a few are mentioned as reference: Angola, Bangladesh, Brazil, People’s Republic of China, Democratic Republic of Congo, Ethiopia, India, Indonesia, Madagascar, Mozambique, Myanmar, Nepal, Nigeria, Philippines, South Sudan, Sri Lanka, Sudan and the United Republic of Tanzania.

Brief history of the disease and treatment

Leprosy was recognized in the ancient civilizations of China, Egypt and India. The first-known written mention of leprosy is dated 600 BC. Throughout history, people afflicted have often been ostracized by their communities and families.Although leprosy was treated differently in the past, the first breakthrough occurred in the 1940s with the development of the drug dapsone, which arrested the disease. But the duration of the treatment was many years and even a lifetime, making it difficult for patients to follow it. In the 1960s, M. leprae started to develop resistance to dapsone, the world’s only known anti-leprosy drug at that time. In the early 1960s, rifampicin and clofazimine, the other two components of recommended multidrug therapy (MDT), were discovered.In 1981, a WHO Study Group recommended MDT. MDT consists of 3 drugs: dapsone, rifampicin and clofazimine, and this drug combination kills the pathogen and cures the patient.Since 1995, WHO provides free MDT for all patients in the world, initially through the drug fund provided by the Nippon Foundation, and since 2000 through the MDT donation provided by Novartis and the Novartis Foundation for Sustainable Development.

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Elimination of leprosy as a public health problem

In 1991 the World Health Assembly passed a resolution to eliminate leprosy by the year 2000. Elimination of leprosy is defined as a prevalence rate of less than 1 case per 10 000 persons. The target was achieved on time and the widespread use of MDT reduced the disease burden dramatically.

Over the past 20 years, more than 14 million leprosy patients have been cured, about 4 million of them since 2000.

The prevalence rate of the disease has dropped by 90%: from 21.1 per 10 000 persons to less than 1 per 10 000 persons in 2000.

A dramatic decrease has been achieved in the global disease burden: from 5.2 million in 1985 to 805 000 in 1995, 753 000 at the end of 1999 and 180 618 cases at the end of 2013.

Leprosy has been eliminated from 119 out of the 122 countries where the disease was considered a public health problem in 1985.

So far, there has been no resistance to antileprosy treatment when used as MDT. Efforts currently focus on eliminating leprosy at a national level in the remaining endemic

countries and at a sub-national level from the others.

Actions and resources required

In order to reach all patients, leprosy treatment needs to be fully integrated into general health services. Moreover, political commitment needs to be sustained in countries where leprosy remains a public health problem. Partners in leprosy elimination also need to ensure that human and financial resources continue to be available.The age-old stigma associated with the disease remains an obstacle to self-reporting and early treatment. The image of leprosy has to be changed at the global, national and local levels. A new environment, in which patients will not hesitate to come forward for diagnosis and treatment at any health facility, must be created.

WHO response

The WHO strategy for leprosy elimination contains the following: ensuring accessible and uninterrupted MDT services available to all patients through flexible

and patient-friendly drug delivery systems; ensuring the sustainability of MDT services by integrating leprosy services into the general

health services and building the ability of general health workers to treat leprosy; encouraging self-reporting and early treatment by promoting community awareness and

changing the image of leprosy; monitoring the performance of MDT services and quality of patients’ care, and the progress

being made towards elimination through national disease surveillance systems. Sustained and committed efforts by the national programmes along with continued support

from national and international partners have led to a decline in the global burden of leprosy. Increased empowerment of people affected by the disease, together with their greater involvement in services and the community, will bring us closer to a world without leprosy.

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Lymphatic filariasis

Fact sheet N°102Updated May 2015

Key facts

Lymphatic filariasis is a parasitic infection that can result in an altered lymphatic system and the abnormal enlargement of body parts, causing pain, severe disability and social stigma.

About 1.23 billion people in 58 countries worldwide are threatened by lymphatic filariasis and require preventive largescale treatment, also known as preventive chemotheraphy, to stop its spread.

Over 120 million people are infected, with about 40 million disfigured and incapacitated by the disease.

Lymphatic filariasis can be eliminated by stopping the spread of infection through preventive chemotherapy with single doses of 2 medicines for persons living in areas where the infection is present.

A basic, recommended package of care can alleviate suffering and prevent further disability among patients.

The disease

Lymphatic filariasis, commonly known as elephantiasis, is a neglected tropical disease. Infection occurs when filarial parasites are transmitted to humans through mosquitoes. Infection is usually acquired in childhood causing hidden damage to the lymphatic system.

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The painful and profoundly disfiguring visible manifestations of the disease, lymphoedema, elephantiasis and scrotal swelling occur later in life and lead to permanent disability. These patients are not only physically disabled, but suffer mental, social and financial losses contributing to stigma and poverty.Currently, 1.23 billion people in 58 countries are living in areas where lymphatic filariasis is transmitted and are at risk of being infected. Approximately 80% of these people are living in the following 10 countries: Bangladesh, Côte d’Ivoire, Democratic Republic of Congo, India, Indonesia, Myanmar, Nigeria, Nepal, Philippines and the United Republic of Tanzania.Globally, an estimated 25 million men suffer with genital disease and over 15 million people are afflicted with lymphoedema. Eliminating lymphatic filariasis can prevent unnecessary suffering and contribute to the reduction of poverty.

Cause and transmission

Lymphatic filariasis is caused by infection with parasites classified as nematodes (roundworms) of the family Filariodidea. There are 3 types of these thread-like filarial worms:

Wuchereria bancrofti, which is responsible for 90% of the cases Brugia malayi, which causes most of the remainder of the cases B. timori, which also causes the disease.

Adult worms lodge in the lymphatic system and disrupt the immune system. The worms can live for an average of 6-8 years and, during their life time, produce millions of microfilariae (immature larvae) that circulate in the blood.Mosquitoes are infected with microfilariae by ingesting blood when biting an infected host. Microfilariae mature into infective larvae within the mosquito. When infected mosquitoes bite people, mature parasite larvae are deposited on the skin from where they can enter the body. The larvae then migrate to the lymphatic vessels where they develop into adult worms, thus continuing a cycle of transmission.Lymphatic filariasis is transmitted by different types of mosquitoes, for example theCulex mosquito that is widespread across urban and semi-urban areas; the Anopheles mainly in rural areas, and Aedes, mainly in endemic islands in the Pacific.


Lymphatic filariasis infection involves asymptomatic, acute, and chronic conditions. The majority of infections are asymptomatic, showing no external signs of infection. These asymptomatic infections still cause damage to the lymphatic system and the kidneys as well as alter the body’s immune system.Acute episodes of local inflammation involving skin, lymph nodes and lymphatic vessels often accompany the chronic lymphoedema or elephantiasis. Some of these episodes are caused by the body's immune response to the parasite. However most are the result of bacterial skin infection where normal defences have been partially lost due to underlying lymphatic damage.When lymphatic filariasis develops into chronic conditions, it leads to lymphoedema (tissue swelling) or elephantiasis (skin/tissue thickening) of limbs and hydrocele (scrotal swelling). Involvement of breasts and genital organs is common. Such body deformities lead to social stigma, as well as financial hardship from loss of income and increased medical expenses. The socioeconomic burdens of isolation and poverty are immense.

WHO's response

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World Health Assembly Resolution 50.29 encourages Member States to eliminate lymphatic filariasis as a public health problem. In response, WHO launched its Global Programme to Eliminate Lymphatic Filariasis (GPELF) in 2000 with the aim of eliminating the disease as a public health problem. In 2012, the WHO NTD Roadmap reconfirmed the target date for achieving elimination as 2020.WHO’s strategy is based on 2 key components:

stopping transmission through large-scale annual treatment of all eligible people in an area or region where infection is present; and

alleviating the suffering caused by lymphatic filariasis through increased morbidity management and disability prevention activities.

Large-scale treatment (preventive chemotherapy)

Elimination of lymphatic filariasis is possible by stopping the spread of the infection. Large-scale treatment involves a single dose of 2 medicines given annually to an entire at-risk population in the following way: albendazole (400 mg) together with ivermectin (150–200 mcg/kg) or with diethylcarbamazine citrate (DEC) (6 mg/kg).These medicines have a limited effect on adult parasites but effectively clear microfilariae from the bloodstream and prevent the spread of parasites to mosquitoes. This recommended large-scale treatment strategy, called preventive chemotherapy, when conducted annually for 4–6 years can interrupt the transmission cycle.At the start of GPELF, 81 countries were considered endemic for lymphatic filariasis. Further epidemiological data indicated that preventive chemotherapy was not required in 9 countries. From 2000 to 2013, over 5 billion treatments were delivered to a targeted population of about 984 million individuals in 56 countries, considerably reducing transmission in many places. Recent research data show that the transmission of lymphatic filariasis in at-risk populations has dropped by 43% since the start of GPELF. The overall economic benefit of the programme during 2000–2007 is conservatively estimated at US$ 24 billion.Currently 73 countries are considered endemic and 17 of these have successfully implemented recommended strategies and are under surveillance to demonstrate that elimination has been achieved.However, preventive chemotherapy has not been delivered to all endemic areas and 28 countries are not on track to achieve elimination targets and stop treatment by 2020.

Morbidity management

Morbidity management and disability prevention are vital for improving public health and should be fully integrated into the health system to ensure sustainability. Surgery can alleviate most cases of hydrocele. Clinical severity of lymphoedema and acute inflammatory episodes can be improved using simple measures of hygiene, skin care, exercise, and elevation of affected limbs. People with lymphoedema must have access to continuing care throughout their lives, both to manage the disease and to prevent progression to more advanced stages.The GPELF aims to provide access to a minimum package of care for every person with associated chronic manifestations of lymphatic filariasis in all areas where the disease is present, thus alleviating suffering and improving their quality of life. Success in 2020 will be achieved if patients have access to the following minimum package of care:

treatment for episodes of adenolymphangitis (ADL), guidance in applying simple measures to manage lymphoedema and hydrocele to prevent

progression of lymphoedema and debilitating, inflammatory episodes of ADL, hydrocele surgery,

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treatment with antifilarial medicines to destroy any remaining worms and microfilariae by preventive chemotherapy or individual treatment.

Vector controlMosquito control is another supplemental strategy supported by WHO. It is used to reduce transmission of lymphatic filariasis and other mosquito-borne infections. Measures such as insecticide-treated nets or indoor residual spraying may help protect people from infection. In some settings, vector control in the absence of preventive chemotherapy has eliminated lymphatic filariasis.


Fact sheet N°94 Reviewed April 2015

Key facts

Malaria is a life-threatening disease caused by parasites that are transmitted to people through the bites of infected mosquitoes.

In 2013, malaria caused an estimated 584 000 deaths (with an uncertainty range of 367 000 to 755 000), mostly among African children.

Malaria is preventable and curable. Increased malaria prevention and control measures are dramatically reducing the malaria

burden in many places. Non-immune travellers from malaria-free areas are very vulnerable to the disease when they

get infected.

According to the latest estimates, released in December 2014, there were about 198 million cases of malaria in 2013 (with an uncertainty range of 124 million to 283 million) and an estimated 584 000 deaths (with an uncertainty range of 367 000 to 755 000). Malaria mortality rates have fallen by 47% globally since 2000, and by 54% in the WHO African Region.Most deaths occur among children living in Africa where a child dies every minute from malaria. Malaria mortality rates among children in Africa have been reduced by an estimated 58% since 2000.Malaria is caused by Plasmodium parasites. The parasites are spread to people through the bites of infected Anopheles mosquitoes, called "malaria vectors", which bite mainly between dusk and dawn.There are four parasite species that cause malaria in humans:

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Plasmodium falciparum Plasmodium vivax Plasmodium malariae Plasmodium ovale.

Plasmodium falciparum and Plasmodium vivax are the most common. Plasmodium falciparum is the most deadly.In recent years, some human cases of malaria have also occurred with Plasmodium knowlesi – a species that causes malaria among monkeys and occurs in certain forested areas of South-East Asia.


Malaria is transmitted exclusively through the bites of Anopheles mosquitoes. The intensity of transmission depends on factors related to the parasite, the vector, the human host, and the environment.About 20 different Anopheles species are locally important around the world. All of the important vector species bite at night. Anopheles mosquitoes breed in water and each species has its own breeding preference; for example some prefer shallow collections of fresh water, such as puddles, rice fields, and hoof prints. Transmission is more intense in places where the mosquito lifespan is longer (so that the parasite has time to complete its development inside the mosquito) and where it prefers to bite humans rather than other animals. For example, the long lifespan and strong human-biting habit of the African vector species is the main reason why about 90% of the world's malaria deaths are in Africa.Transmission also depends on climatic conditions that may affect the number and survival of mosquitoes, such as rainfall patterns, temperature and humidity. In many places, transmission is seasonal, with the peak during and just after the rainy season. Malaria epidemics can occur when climate and other conditions suddenly favour transmission in areas where people have little or no immunity to malaria. They can also occur when people with low immunity move into areas with intense malaria transmission, for instance to find work, or as refugees.Human immunity is another important factor, especially among adults in areas of moderate or intense transmission conditions. Partial immunity is developed over years of exposure, and while it never provides complete protection, it does reduce the risk that malaria infection will cause severe disease. For this reason, most malaria deaths in Africa occur in young children, whereas in areas with less transmission and low immunity, all age groups are at risk.


Malaria is an acute febrile illness. In a non-immune individual, symptoms appear seven days or more (usually 10–15 days) after the infective mosquito bite. The first symptoms – fever, headache, chills and vomiting – may be mild and difficult to recognize as malaria. If not treated within 24 hours, P. falciparum malaria can progress to severe illness often leading to death. Children with severe malaria frequently develop one or more of the following symptoms: severe anaemia, respiratory distress in relation to metabolic acidosis, or cerebral malaria. In adults, multi-organ involvement is also frequent. In malaria endemic areas, persons may develop partial immunity, allowing asymptomatic infections to occur.For both P. vivax and P. ovale, clinical relapses may occur weeks to months after the first infection, even if the patient has left the malarious area. These new episodes arise from dormant liver forms known as hypnozoites (absent in P. falciparum and P. malariae); special treatment – targeted at these liver stages – is required for a complete cure.

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Who is at risk?

Approximately half of the world's population is at risk of malaria. Most malaria cases and deaths occur in sub-Saharan Africa. However, Asia, Latin America, and to a lesser extent the Middle East and parts of Europe are also affected. In 2014, 97 countries and territories had ongoing malaria transmission.Specific population risk groups include:

young children in stable transmission areas who have not yet developed protective immunity against the most severe forms of the disease;

non-immune pregnant women as malaria causes high rates of miscarriage and can lead to maternal death;

semi-immune pregnant women in areas of high transmission. Malaria can result in miscarriage and low birth weight, especially during first and second pregnancies;

semi-immune HIV-infected pregnant women in stable transmission areas, during all pregnancies. Women with malaria infection of the placenta also have a higher risk of passing HIV infection to their newborns;

people with HIV/AIDS; international travellers from non-endemic areas because they lack immunity; immigrants from endemic areas and their children living in non-endemic areas and returning

to their home countries to visit friends and relatives are similarly at risk because of waning or absent immunity.

Diagnosis and treatment

Early diagnosis and treatment of malaria reduces disease and prevents deaths. It also contributes to reducing malaria transmission.The best available treatment, particularly for P. falciparum malaria, is artemisinin-based combination therapy (ACT).WHO recommends that all cases of suspected malaria be confirmed using parasite-based diagnostic testing (either microscopy or rapid diagnostic test) before administering treatment. Results of parasitological confirmation can be available in 15 minutes or less. Treatment solely on the basis of symptoms should only be considered when a parasitological diagnosis is not possible. More detailed recommendations are available in the "Guidelines for the treatment of malaria" (second edition). An updated edition will be published in 2015.

Antimalarial drug resistance

Resistance to antimalarial medicines is a recurring problem. Resistance of P. falciparum to previous generations of medicines, such as chloroquine and sulfadoxine-pyrimethamine (SP), became widespread in the 1970s and 1980s, undermining malaria control efforts and reversing gains in child survival.In recent years, parasite resistance to artemisinins has been detected in 5 countries of the Greater Mekong subregion: Cambodia, Laos, Myanmar, Thailand and Viet Nam. While there are likely many factors that contribute to the emergence and spread of resistance, the use of oral artemisinins alone, as monotherapy, is thought to be an important driver. When treated with an oral artemisinin-based monotherapy, patients may discontinue treatment prematurely following the rapid disappearance of malaria symptoms. This results in incomplete treatment, and such patients still have persistent

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parasites in their blood. Without a second drug given as part of a combination (as is provided with an ACT), these resistant parasites survive and can be passed on to a mosquito and then another person.If resistance to artemisinins develops and spreads to other large geographical areas, the public health consequences could be dire.WHO recommends the routine monitoring of antimalarial drug resistance, and supports countries to strengthen their efforts in this important area of work.More comprehensive recommendations are available in the "WHO Global Plan for Artemisinin Resistance Containment (GPARC)", which was released in 2011. For countries in the Greater Mekong subregion, WHO has issued a regional framework for action titled "Emergency response to artemisinin resistance in the Greater Mekong subregion" in 2013.


Vector control is the main way to reduce malaria transmission at the community level. It is the only intervention that can reduce malaria transmission from very high levels to close to zero.For individuals, personal protection against mosquito bites represents the first line of defence for malaria prevention.Two forms of vector control are effective in a wide range of circumstances.

Insecticide-treated mosquito nets (ITNs)Long-lasting insecticidal nets (LLINs) are the preferred form of ITNs for public health distribution programmes. WHO recommends coverage for all at-risk persons; and in most settings. The most cost effective way to achieve this is through provision of free LLINs, so that everyone sleeps under a LLIN every night.

Indoor spraying with residual insecticidesIndoor residual spraying (IRS) with insecticides is a powerful way to rapidly reduce malaria transmission. Its full potential is realized when at least 80% of houses in targeted areas are sprayed. Indoor spraying is effective for 3–6 months, depending on the insecticide used and the type of surface on which it is sprayed. DDT can be effective for 9–12 months in some cases. Longer-lasting forms of existing IRS insecticides, as well as new classes of insecticides for use in IRS programmes, are under development.Antimalarial medicines can also be used to prevent malaria. For travellers, malaria can be prevented through chemoprophylaxis, which suppresses the blood stage of malaria infections, thereby preventing malaria disease. In addition, WHO recommends intermittent preventive treatment with sulfadoxine-pyrimethamine for pregnant women living in high transmission areas, at each scheduled antenatal visit after the first trimester. Similarly, for infants living in high-transmission areas of Africa, 3 doses of intermittent preventive treatment with sulfadoxine-pyrimethamine is recommended delivered alongside routine vaccinations. In 2012, WHO recommended Seasonal Malaria Chemoprevention as an additional malaria prevention strategy for areas of the Sahel sub-Region of Africa. The strategy involves the administration of monthly courses of amodiaquine plus sulfadoxine-pyrimethamine to all children under 5 years of age during the high transmission season.

Insecticide resistance

Much of the success to date in controlling malaria is due to vector control. Vector control is highly dependent on the use of pyrethroids, which are the only class of insecticides currently recommended for ITNs or LLINs. In recent years, mosquito resistance to pyrethroids has emerged in many countries.

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In some areas, resistance to all 4 classes of insecticides used for public health has been detected. Fortunately, this resistance has only rarely been associated with decreased efficacy, and LLINs and IRS remain highly effective tools in almost all settings.However, countries in sub-Saharan Africa and India are of significant concern. These countries are characterized by high levels of malaria transmission and widespread reports of insecticide resistance. The development of new, alternative insecticides is a high priority and several promising products are in the pipeline. Development of new insecticides for use on bed nets is a particular priority.Detection of insecticide resistance should be an essential component of all national malaria control efforts to ensure that the most effective vector control methods are being used. The choice of insecticide for IRS should always be informed by recent, local data on the susceptibility target vectors.In order to ensure a timely and coordinated global response to the threat of insecticide resistance, WHO has worked with a wide range of stakeholders to develop the "Global Plan for Insecticide Resistance Management in malaria vectors" (GPIRM), which was released in May 2012. The GPIRM puts forward a five-pillar strategy calling on the global malaria community to:

plan and implement insecticide resistance management strategies in malaria-endemic countries;

ensure proper and timely entomological and resistance monitoring, and effective data management;

develop new and innovative vector control tools; fill gaps in knowledge on mechanisms of insecticide resistance and the impact of current

insecticide resistance management approaches; and ensure that enabling mechanisms (advocacy as well as human and financial resources) are in



Tracking progress is a major challenge in malaria control. In 2012, malaria surveillance systems detected only around 14% of the estimated global number of cases. Stronger malaria surveillance systems are urgently needed to enable a timely and effective malaria response in endemic regions, to prevent outbreaks and resurgences, to track progress, and to hold governments and the global malaria community accountable.


Malaria elimination is defined as interrupting local mosquito-borne malaria transmission in a defined geographical area, i.e. zero incidence of locally contracted cases. Malaria eradication is defined as the permanent reduction to zero of the worldwide incidence of malaria infection caused by a specific agent; i.e. applies to a particular malaria parasite species.On the basis of reported cases for 2013, 55 countries are on track to reduce their malaria case incidence rates by 75%, in line with World Health Assembly targets for 2015. Large-scale use of WHO-recommended strategies, currently available tools, strong national commitments, and coordinated efforts with partners, will enable more countries – particularly those where malaria transmission is low and unstable – to reduce their disease burden and progress towards elimination.In recent years, 4 countries have been certified by the WHO Director-General as having eliminated malaria: United Arab Emirates (2007), Morocco (2010), Turkmenistan (2010), and Armenia (2011).

Vaccines against malaria

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There are currently no licensed vaccines against malaria or any other human parasite. One research vaccine against P. falciparum, known as RTS, S/AS01, is most advanced. This vaccine has been evaluated in a large clinical trial in 7 countries in Africa and has been submitted to the European Medicines Agency under art. 58 for regulatory review. A WHO recommendation for use will depend on the final results from the large clinical trial and a positive regulatory review. The recommendation as to whether or not this vaccine should be added to existing malaria control tools is expected in late 2015.

WHO response

The WHO Global Malaria Programme (GMP) is responsible for charting the course for malaria control and elimination through:

setting, communicating and promoting the adoption of evidence-based norms, standards, policies, technical strategies, and guidelines;

keeping independent score of global progress; developing approaches for capacity building, systems strengthening, and surveillance; identifying threats to malaria control and elimination as well as new areas for action. GMP serves as the secretariat for the Malaria Policy Advisory Committee (MPAC), a group of

15 global malaria experts appointed following an open nomination process. The MPAC, which meets twice yearly, provides independent advice to WHO to develop policy recommendations for the control and elimination of malaria. The mandate of MPAC is to provide strategic advice and technical input, and extends to all aspects of malaria control and elimination, as part of a transparent, responsive and credible policy setting process.

WHO is also a co-founder and host of the Roll Back Malaria partnership, which is the global framework to implement coordinated action against malaria. The partnership mobilizes for action and resources and forges consensus among partners. It is comprised of over 500 partners, including malaria endemic countries, development partners, the private sector, nongovernmental and community-based organizations, foundations, and research and academic institutions.

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Fact sheet N°286 Reviewed February 2015

Key facts

Measles is one of the leading causes of death among young children even though a safe and cost-effective vaccine is available.

In 2013, there were 145 700 measles deaths globally – about 400 deaths every day or 16 deaths every hour.

Measles vaccination resulted in a 75% drop in measles deaths between 2000 and 2013 worldwide.

In 2013, about 84% of the world's children received one dose of measles vaccine by their first birthday through routine health services – up from 73% in 2000.

During 2000-2013, measles vaccination prevented an estimated 15.6 million deaths making measles vaccine one of the best buys in public health.

Measles is a highly contagious, serious disease caused by a virus. In 1980, before widespread vaccination, measles caused an estimated 2.6 million deaths each year.The disease remains one of the leading causes of death among young children globally, despite the availability of a safe and effective vaccine. Approximately 145 700 people died from measles in 2013 – mostly children under the age of 5.Measles is caused by a virus in the paramyxovirus family and it is normally passed through direct contact and through the air. The virus infects the mucous membranes, then spreads throughout the body. Measles is a human disease and is not known to occur in animals.

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Accelerated immunization activities have had a major impact on reducing measles deaths. During 2000-2013, measles vaccination prevented an estimated 15.6 million deaths. Global measles deaths have decreased by 75% from an estimated 544 200 in 2000 to 145 700 in 2013.

Signs and symptoms

The first sign of measles is usually a high fever, which begins about 10 to 12 days after exposure to the virus, and lasts 4 to 7 days. A runny nose, a cough, red and watery eyes, and small white spots inside the cheeks can develop in the initial stage. After several days, a rash erupts, usually on the face and upper neck. Over about 3 days, the rash spreads, eventually reaching the hands and feet. The rash lasts for 5 to 6 days, and then fades. On average, the rash occurs 14 days after exposure to the virus (within a range of 7 to 18 days).Most measles-related deaths are caused by complications associated with the disease. Complications are more common in children under the age of 5, or adults over the age of 20. The most serious complications include blindness, encephalitis (an infection that causes brain swelling), severe diarrhoea and related dehydration, ear infections, or severe respiratory infections such as pneumonia. Severe measles is more likely among poorly nourished young children, especially those with insufficient vitamin A, or whose immune systems have been weakened by HIV/AIDS or other diseases.In populations with high levels of malnutrition and a lack of adequate health care, up to 10% of measles cases result in death. Women infected while pregnant are also at risk of severe complications and the pregnancy may end in miscarriage or preterm delivery. People who recover from measles are immune for the rest of their lives.

Who is at risk?Unvaccinated young children are at highest risk of measles and its complications, including death. Unvaccinated pregnant women are also at risk. Any non-immune person (who has not been vaccinated or was vaccinated but did not develop immunity) can become infected.Measles is still common in many developing countries – particularly in parts of Africa and Asia. The overwhelming majority (more than 95%) of measles deaths occur in countries with low per capita incomes and weak health infrastructures.Measles outbreaks can be particularly deadly in countries experiencing or recovering from a natural disaster or conflict. Damage to health infrastructure and health services interrupts routine immunization, and overcrowding in residential camps greatly increases the risk of infection.


The highly contagious virus is spread by coughing and sneezing, close personal contact or direct contact with infected nasal or throat secretions.The virus remains active and contagious in the air or on infected surfaces for up to 2 hours. It can be transmitted by an infected person from 4 days prior to the onset of the rash to 4 days after the rash erupts.Measles outbreaks can result in epidemics that cause many deaths, especially among young, malnourished children. In countries where measles has been largely eliminated, cases imported from other countries remain an important source of infection.


No specific antiviral treatment exists for measles virus.

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Severe complications from measles can be avoided through supportive care that ensures good nutrition, adequate fluid intake and treatment of dehydration with WHO-recommended oral rehydration solution. This solution replaces fluids and other essential elements that are lost through diarrhoea or vomiting. Antibiotics should be prescribed to treat eye and ear infections, and pneumonia.All children in developing countries diagnosed with measles should receive two doses of vitamin A supplements, given 24 hours apart. This treatment restores low vitamin A levels during measles that occur even in well-nourished children and can help prevent eye damage and blindness. Vitamin A supplements have been shown to reduce the number of deaths from measles by 50%.


Routine measles vaccination for children, combined with mass immunization campaigns in countries with high case and death rates, are key public health strategies to reduce global measles deaths. The measles vaccine has been in use for 50 years. It is safe, effective and inexpensive. It costs approximately one US dollar to immunize a child against measles.The measles vaccine is often incorporated with rubella and/or mumps vaccines in countries where these illnesses are problems. It is equally effective in the single or combined form. Adding rubella to measles vaccine increases the cost only slightly, and allows for shared delivery and administration costs.In 2013, about 84% of the world's children received 1 dose of measles vaccine by their first birthday through routine health services – up from 73% in 2000. Two doses of the vaccine are recommended to ensure immunity and prevent outbreaks, as about 15% of vaccinated children fail to develop immunity from the first dose.

WHO response

The fourth Millennium Development Goal (MDG 4) aims to reduce the under-five mortality rate by two-thirds between 1990 and 2015. Recognizing the potential of measles vaccination to reduce child mortality, and given that measles vaccination coverage can be considered a marker of access to child health services, routine measles vaccination coverage has been selected as an indicator of progress towards achieving MDG 4.Overwhelming evidence demonstrates the benefit of providing universal access to measles and rubella-containing vaccines.By 2013, the global push to improve vaccine coverage resulted in a 75% reduction in deaths. During 2000-2013, with support from the Measles & Rubella Initiative (M&R Initiative), measles vaccination prevented an estimated 15.6 million. During 2013, about 205 million children were vaccinated against measles during mass vaccination campaigns in 34 countries. All WHO Regions have now established goals to eliminate this preventable killer disease by 2020.The M&R Initiative is a collaborative effort of WHO, UNICEF, the American Red Cross, the United States Centers for Disease Control and Prevention, and the United Nations Foundation to support countries to achieve measles and rubella control goals.

M&R Initiative In 2012, the MR Initiative launched a new Global Measles and Rubella Strategic Plan which

covers the period 2012-2020. The Plan includes new global goals for 2015 and 2020: By the end of 2015

To reduce global measles deaths by at least 95% compared with 2000 levels.

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To achieve regional measles and rubella/congenital rubella syndrome (CRS) elimination goals.

By the end of 2020

To achieve measles and rubella elimination in at least 5 WHO regions. The strategy focuses on the implementation of 5 core components: achieve and maintain high vaccination coverage with 2 doses of measles- and rubella-

containing vaccines; monitor the disease using effective surveillance, and evaluate programmatic efforts to

ensure progress and the positive impact of vaccination activities; develop and maintain outbreak preparedness, rapid response to outbreaks and the effective

treatment of cases; communicate and engage to build public confidence and demand for immunization; perform the research and development needed to support cost-effective action and improve

vaccination and diagnostic tools. Implementation of the Strategic Plan can protect and improve the lives of children and their

mothers throughout the world, rapidly and sustainably. The Plan provides clear strategies for country immunization managers, working with domestic and international partners, to achieve the 2015 and 2020 measles and rubella control and elimination goals. It builds on years of experience in implementing immunization programmes and incorporates lessons from accelerated measles control and polio eradication initiatives.

Based on current trends and performance, global immunization experts concluded that the 2015 measles milestones and elimination goals will not be achieved on time. Resuming progress will require countries and immunization partners to raise the visibility of measles elimination, address barriers to measles vaccination, and make substantial and sustained additional investments to strengthen health systems and achieve equitable access to immunization services.

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Middle East respiratory syndrome coronavirus (MERS-CoV)

Fact sheet N°401June 2015

Key facts

Middle East respiratory syndrome (MERS) is a viral respiratory disease caused by a novel coronavirus (MERS‐CoV) that was first identified in Saudi Arabia in 2012.Coronaviruses are a large family of viruses that can cause diseases ranging from the common cold to Severe Acute Respiratory Syndrome (SARS).Typical MERS symptoms include fever, cough and shortness of breath. Pneumonia is common, but not always present. Gastrointestinal symptoms, including diarrhoea, have also been reported.Approximately 36% of reported patients with MERS have died.Although the majority of human cases of MERS have been attributed to human-to-human infections, camels are likely to be a major reservoir host for MERS-CoV and an animal source of MERS infection in humans. However, the exact role of camels in transmission of the virus and the exact route(s) of transmission are unknown.The virus does not seem to pass easily from person to person unless there is close contact, such as occurs when providing unprotected care to a patient.


The clinical spectrum of MERS-CoV infection ranges from no symptoms (asymptomatic) or mild respiratory symptoms to severe acute respiratory disease and death. A typical presentation of MERS-CoV disease is fever, cough and shortness of breath. Pneumonia is a common finding, but not always

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present. Gastrointestinal symptoms, including diarrhoea, have also been reported. Severe illness can cause respiratory failure that requires mechanical ventilation and support in an intensive care unit. Approximately 36% of reported patients with MERS-CoV have died. The virus appears to cause more severe disease in older people, people with weakened immune systems, and those with chronic diseases such as cancer, chronic lung disease and diabetes.

Source of the virus

MERS-CoV is a zoonotic virus that is transmitted from animals to humans. The origins of the virus are not fully understood but, according to the analysis of different virus genomes, it is believed that it originated in bats and was transmitted to camels sometime in the distant past.


Non-human to human transmission: The route of transmission from animals to humans is not fully understood, but camels are likely to be a major reservoir host for MERS-CoV and an animal source of infection in humans. Strains of MERS-CoV that are identical to human strains have been isolated from camels in several countries, including Egypt, Oman, Qatar, and Saudi Arabia.Human-to-human transmission: The virus does not appear to pass easily from person to person unless there is close contact, such as providing unprotected care to an infected patient. There have been clusters of cases in healthcare facilities, where human-to-human transmission appears to be more probable, especially when infection prevention and control practices are inadequate. Thus far, no sustained community transmission has been documented.The virus appears to be circulating throughout the Arabian Peninsula, primarily in Saudi Arabia, where the majority of cases (>85%) have been reported since 2012. Several cases have been reported outside the Middle East. Most of these infections are believed to have been acquired in the Middle East, and then exported outside the region. The ongoing outbreak in the Republic of Korea is the largest outbreak outside of the Middle East, and while concerning, there is no evidence of sustained human to human transmission in the Republic of Korea. For all other exported cases, no secondary or limited secondary transmission has been reported in countries with exported cases.

Prevention and treatment

No vaccine or specific treatment is currently available. Treatment is supportive and based on the patient’s clinical condition.As a general precaution, anyone visiting farms, markets, barns, or other places where camels and other animals are present should practice general hygiene measures, including regular hand washing before and after touching animals, and should avoid contact with sick animals.The consumption of raw or undercooked animal products, including milk and meat, carries a high risk of infection from a variety of organisms that might cause disease in humans. Animal products that are processed appropriately through cooking or pasteurization are safe for consumption, but should also be handled with care to avoid cross contamination with uncooked foods. Camel meat and camel milk are nutritious products that can continue to be consumed after pasteurization, cooking, or other heat treatments.Until more is understood about MERS-CoV, people with diabetes, renal failure, chronic lung disease, and immunocompromised persons are considered to be at high risk of severe disease from MERS-CoV infection. These people should avoid contact with camels, drinking raw camel milk or camel urine, or eating meat that has not been properly cooked.

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Health-care facilities

Transmission of the virus has occurred in health‐care facilities in several countries, including from patients to health‐care providers and between patients in a health care setting before MERS-CoV was diagnosed. It is not always possible to identify patients with MERS‐CoV early or without testing because symptoms and other clinical features may be non‐specific.Infection prevention and control measures are critical to prevent the possible spread of MERS‐CoV in health‐care facilities. Facilities that provide care for patients suspected or confirmed to be infected with MERS‐CoV should take appropriate measures to decrease the risk of transmission of the virus from an infected patient to other patients, health‐care workers, or visitors. Health‐care workers should be educated and trained in infection prevention and control and should refresh these skills regularly.


WHO does not recommend the application of any travel or trade restrictions or entry screening related to MERS-CoV.

WHO response

WHO is working with clinicians and scientists in affected countries and internationally to gather and share scientific evidence to better understand the virus and the disease it causes, and to determine outbreak response priorities, treatment strategies, and clinical management approaches. The Organization is also working with countries to develop public health prevention strategies to combat the virus.Together with affected countries and international technical partners and networks, WHO is coordinating the global health response to MERS, including: the provision of updated information on the situation; conducting risk assessments and joint investigations with national authorities; convening scientific meetings; and developing guidance and training for health authorities and technical health agencies on interim surveillance recommendations, laboratory testing of cases, infection prevention and control, and clinical management.The Director‐General has convened an Emergency Committee under the International Health Regulations (2005) to advise her as to whether this event constitutes a Public Health Emergency of International Concern (PHEIC) and on the public health measures that should be taken. The Committee has met a number of times since the disease was first identified. WHO encourages all Member States to enhance their surveillance for severe acute respiratory infections (SARI) and to carefully review any unusual patterns of SARI or pneumonia cases.Countries, whether or not MERS cases have been reported in them, should maintain a high level of vigilance, especially those with large numbers of travellers or migrant workers returning from the Middle East. Surveillance should continue to be enhanced in these countries according to WHO guidelines, along with infection prevention and control procedures in health-care facilities. WHO continues to request that Member States report to WHO all confirmed and probable cases of infection with MERS-CoV together with information about their exposure, testing, and clinical course to inform the most effective international preparedness and response.

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Fact sheet N°331Updated November 2014

Key facts

Pneumonia is the leading infectious cause of death in children worldwide, accounting for 15% of all deaths of children under 5 years old.

Pneumonia killed an estimated 935 000 children under the age of five in 2013. Pneumonia can be caused by viruses, bacteria or fungi. Pneumonia can be prevented by immunization, adequate nutrition and by addressing

environmental factors. Pneumonia caused by bacteria can be treated with antibiotics, but only one third of children

with pneumonia receive the antibiotics they need.

Pneumonia is a form of acute respiratory infection that affects the lungs. The lungs are made up of small sacs called alveoli, which fill with air when a healthy person breathes. When an individual has pneumonia, the alveoli are filled with pus and fluid, which makes breathing painful and limits oxygen intake.Pneumonia is the single largest infectious cause of death in children worldwide. Pneumonia killed an estimated 935 000 children under the age of five in 2013, accounting for 15% of all deaths of children under five years old. Pneumonia affects children and families everywhere, but is most prevalent in

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South Asia and sub-Saharan Africa. Children can be protected from pneumonia, it can be prevented with simple interventions, and treated with low-cost, low-tech medication and care.Causes

Pneumonia is caused by a number of infectious agents, including viruses, bacteria and fungi. The most common are:

Streptococcus pneumoniae – the most common cause of bacterial pneumonia in children;Haemophilus influenzae type b (Hib) – the second most common cause of bacterial pneumonia;respiratory syncytial virus is the most common viral cause of pneumonia;in infants infected with HIV, Pneumocystis jiroveci is one of the commonest causes of pneumonia, responsible for at least one quarter of all pneumonia deaths in HIV-infected infants.


Pneumonia can be spread in a number of ways. The viruses and bacteria that are commonly found in a child's nose or throat, can infect the lungs if they are inhaled. They may also spread via air-borne droplets from a cough or sneeze. In addition, pneumonia may spread through blood, especially during and shortly after birth. More research needs to be done on the different pathogens causing pneumonia and the ways they are transmitted, as this is of critical importance for treatment and prevention.

Presenting features

The presenting features of viral and bacterial pneumonia are similar. However, the symptoms of viral pneumonia may be more numerous than the symptoms of bacterial pneumonia. In children under 5 years of age, who have cough and/or difficult breathing, with or without fever, pneumonia is diagnosed by the presence of either fast breathing or lower chest wall indrawing where their chest moves in or retracts during inhalation (in a healthy person, the chest expands during inhalation). Wheezing is more common in viral infections.Very severely ill infants may be unable to feed or drink and may also experience unconsciousness, hypothermia and convulsions.

Risk factors

While most healthy children can fight the infection with their natural defences, children whose immune systems are compromised are at higher risk of developing pneumonia. A child's immune system may be weakened by malnutrition or undernourishment, especially in infants who are not exclusively breastfed.Pre-existing illnesses, such as symptomatic HIV infections and measles, also increase a child's risk of contracting pneumonia.The following environmental factors also increase a child's susceptibility to pneumonia:

indoor air pollution caused by cooking and heating with biomass fuels (such as wood or dung)

living in crowded homes parental smoking.


Pneumonia should be treated with antibiotics. The antibiotic of choice is amoxicillin dispersable tablets. Most cases of pneumonia require oral antibiotics, which are often prescribed at a health

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centre. These cases can also be diagnosed and treated with inexpensive oral antibiotics at the community level by trained community health workers. Hospitalization is recommended only for severe cases of pneumonia, and for all cases of pneumonia in infants younger than 2 months of age.


Preventing pneumonia in children is an essential component of a strategy to reduce child mortality. Immunization against Hib, pneumococcus, measles and whooping cough (pertussis) is the most effective way to prevent pneumonia.Adequate nutrition is key to improving children's natural defences, starting with exclusive breastfeeding for the first 6 months of life. In addition to being effective in preventing pneumonia, it also helps to reduce the length of the illness if a child does become ill.Addressing environmental factors such as indoor air pollution (by providing affordable clean indoor stoves, for example) and encouraging good hygiene in crowded homes also reduces the number of children who fall ill with pneumonia.In children infected with HIV, the antibiotic cotrimoxazole is given daily to decrease the risk of contracting pneumonia.

Economic costs

The cost of antibiotic treatment for all children with pneumonia in 66 of the countdown to 2015 countries for maternal, newborn and child survival is estimated at around US$ 109 million per year. The price includes the antibiotics and diagnostics for pneumonia management.

WHO response

The WHO and UNICEF integrated Global action plan for pneumonia and diarrhoea (GAPPD) aims to accelerate pneumonia control with a combination of interventions to protect, prevent, and treat pneumonia in children with actions to:

protect children from pneumonia including promoting exclusive breastfeeding and adequate complementary feeding;

prevent pneumonia with vaccinations, hand washing with soap, reducing household air pollution, HIV prevention and cotrimoxazole prophylaxis for HIV-infected and exposed children;

treat pneumonia focusing on making sure that every sick child has access to the right kind of care -- either from a community-based health worker, or in a health facility if the disease is severe -- and can get the antibiotics and oxygen they need to get well;A number of countries including Bangladesh, India, Uganda and Zambia have developed district, state and national plans to intensify actions for the control of pneumonia and diarrhoea.

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Fact Sheet N°99Updated September 2015

Key facts

Rabies is a vaccine-preventable viral disease which occurs in more than 150 countries and territories.

Dogs are the source of the vast majority of human rabies deaths. Rabies elimination is feasible by vaccinating dogs. Infection causes tens of thousands of deaths every year, mostly in Asia and Africa. 40% of people who are bitten by suspect rabid animals are children under 15 years of age. Immediate wound cleansing with soap and water after contact with a suspect rabid animal

can be life-saving. Every year, more than 15 million people worldwide receive a post-bite vaccination to prevent

the disease; this is estimated to prevent hundreds of thousands of rabies deaths annually.

Rabies is an infectious viral disease that is almost always fatal following the onset of clinical signs. In more than 99% of human cases, the rabies virus is transmitted by domestic dogs. Rabies affects domestic and wild animals, and is spread to people through bites or scratches, usually via saliva.

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Rabies is present on all continents with the exception of Antarctica, but more than 95% of human deaths occur in Asia and Africa.Rabies is a neglected disease of poor and vulnerable populations whose deaths are rarely reported and where human vaccines and immunoglobulin are not readily available or accessible. It occurs mainly in remote rural communities where children between the age of 5–14 years are the most frequent victims.The average cost of rabies post-exposure prophylaxis (PEP) can be the cost of catastrophic expenses for poor populations, since a course of PEP can cost US$ 40 in Africa and US$ 49 in Asia, where the average daily income is about US$ 1–2 per person.


Eliminating rabies in dogsRabies is a vaccine-preventable disease. Vaccinating dogs is the most cost-effective strategy for preventing rabies in people. Dog vaccination will drive down not only the deaths attributable to rabies but also the need for PEP as a part of dogbite patient care.

Preventive immunization in peopleThe same safe and effective vaccines can be used for pre-exposure immunization. This is recommended for travellers spending a lot of time outdoors, especially in rural areas, involved in activities such as bicycling, camping, or hiking as well as for long-term travellers and expatriates living in areas with a significant risk of exposure.Pre-exposure immunization is also recommended for people in certain high-risk occupations such as laboratory workers dealing with live rabies virus and other rabies-related viruses (lyssaviruses), and people involved in any activities that might bring them professionally or otherwise into direct contact with bats, carnivores, and other mammals in rabies-affected areas. As children are considered at higher risk because they tend to play with animals, may receive more severe bites, or may not report bites, their immunization could be considered if living in or visiting high-risk areas.


The incubation period for rabies is typically 1–3 months, but may vary from <1 week to >1 year. The initial symptoms of rabies are fever and often pain or an unusual or unexplained tingling, pricking or burning sensation (paraesthesia) at the wound site. As the virus spreads through the central nervous system, progressive, fatal inflammation of the brain and spinal cord develops.Two forms of the disease can follow. People with furious rabies exhibit signs of hyperactivity, excited behaviour, hydrophobia and sometimes aerophobia. After a few days, death occurs by cardiorespiratory arrest.Paralytic rabies accounts for about 30% of the total number of human cases. This form of rabies runs a less dramatic and usually longer course than the furious form. The muscles gradually become paralyzed, starting at the site of the bite or scratch. A coma slowly develops, and eventually death occurs. The paralytic form of rabies is often misdiagnosed, contributing to the under-reporting of the disease.


No tests are available to diagnose rabies infection in humans before the onset of clinical disease, and unless the rabies-specific signs of hydrophobia or aerophobia are present, the clinical diagnosis may be difficult. Human rabies can be confirmedintra-vitam and post mortem by various diagnostic

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techniques aimed at detecting whole virus, viral antigens or nucleic acids in infected tissues (brain, skin, urine or saliva).


People are usually infected following a deep bite or scratch by an infected animal. Dogs are the main host and transmitter of rabies. They are the cause of human rabies deaths in Asia and Africa.Bats are the source of most human rabies deaths in the Americas. Bat rabies has also recently emerged as a public health threat in Australia and western Europe. Human deaths following exposure to foxes, raccoons, skunks, jackals, mongooses and other wild carnivore host species are very rare.Transmission can also occur when infectious material – usually saliva – comes into direct contact with human mucosa or fresh skin wounds. Human-to-human transmission by bite is theoretically possible but has never been confirmed.Rarely, rabies may be contracted by inhalation of virus-containing aerosol or via transplantation of an infected organ. Ingestion of raw meat or other tissues from animals infected with rabies is not a source of human infection.

Post-exposure prophylaxis (PEP)

Post-exposure prophylaxis (PEP) means the treatment of a bite victim that is started immediately after exposure to rabies in order to prevent rabies infection. This consists of:

local treatment of the wound, initiated as soon as possible after exposure; a course of potent and effective rabies vaccine that meets WHO standards; and the administration of rabies immunoglobulin, if indicated. Effective treatment soon after exposure to rabies can prevent the onset of symptoms and


Local treatment of the woundThis involves first-aid of the wound that includes immediate and thorough flushing and washing of the wound for a minimum of 15 minutes with soap and water, detergent, povidone iodine or other substances that kill the rabies virus.

Recommended PEPDepending on the severity of the contact administering with the suspected rabid animal, administration of PEP is recommended as follows (see table):

Table: Categories of contact and recommended post-exposure prophylaxis (PEP)

Categories of contact with suspect rabid animal

Post-exposure prophylaxis measures

Category I – touching or feeding animals, licks on intact skin None

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Table: Categories of contact and recommended post-exposure prophylaxis (PEP)

Category II – nibbling of uncovered skin, minor scratches or abrasions without bleeding

Immediate vaccination and local treatment of the wound

Category III – single or multiple transdermal bites or scratches, licks on broken skin; contamination of mucous membrane with saliva from licks, contacts with bats.

Immediate vaccination and administration of rabies immunoglobulin; local treatment of the wound

All category II and III exposures assessed as carrying a risk of developing rabies require PEP. This risk is increased if:

the biting mammal is a known rabies reservoir or vector species; the animal looks sick or displays an abnormal behaviour; a wound or mucous membrane was contaminated by the animal’s saliva; the bite was unprovoked; and the animal has not been vaccinated. In developing countries, the vaccination status of the suspected animal alone should not be

considered when deciding whether to initiate prophylaxis or not.

The Organization continues to promote human rabies prevention through the elimination of rabies in dogs as well as a wider use of the intradermal route for PEP which reduces volume and thereby the cost of cell-cultured vaccine by 60% to 80%.

WHO response

WHO, in close collaboration with the Food and Agriculture Organization of the United Nations (FAO), the World Organisation for Animal Health (OIE) and the Global Alliance for Rabies Control, is raising awareness of and commitment to overcoming this persistent zoonosis in endemic countries.Great strides have been made in the Philippines, South Africa and Tanzania where a project is underway as part of a Bill & Melinda Gates Foundation project led by WHO. The key towards sustaining and expanding the rabies programmes to new territories and countries has been to start small, demonstrate success and cost-effectiveness, and ensure community engagement.Stockpiles of dog and human rabies vaccine have had a catalytic effect on rabies elimination efforts in countries.Rabies transmitted by dogs has been eliminated in many Latin American countries, including Chile, Costa Rica, Panama, Uruguay, most of Argentina, the states of São Paulo and Rio de Janeiro in Brazil, and large parts of Mexico and Peru.Many countries in the WHO South-East Asia Region have embarked on elimination campaigns in line with the target of regional elimination by 2020. Bangladesh launched an elimination programme in 2010 and, through the management of dog bites, mass dog vaccination and increased availability of vaccines free of charge, human rabies deaths decreased by 50% during 2010–2014.

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Fact sheet N°115Updated May 2015

Key facts

Schistosomiasis is an acute and chronic disease caused by parasitic worms. People are infected during routine agricultural, domestic, occupational and recreational

activities which expose them to infested water. Lack of hygiene and certain play habits of school-aged children such as swimming or fishing

in infested water make them especially vulnerable to infection. Schistosomiasis control focuses on reducing disease through periodic, large-scale population

treatment with praziquantel; a more comprehensive approach including potable water, adequate sanitation and snail control would also reduce transmission.

At least 261 million people required preventive treatment for schistosomiasis in 2013.

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More than 40 million people were treated for schistosomiasis in 2013.

Schistosomiasis is an acute and chronic parasitic disease caused by blood flukes (trematode worms) of the genus Schistosoma. At least 261 million people required preventive treatment in 2013. Preventive treatment, which should be repeated over a number of years, will reduce and prevent morbidity. Schistosomiasis transmission has been reported from 78 countries. However, preventive chemotherapy for schistosomiasis, where people and communities are targeted for large scale treatment, is only required in 52 endemic countries with moderate to high transmission.


Transmission occurs when people suffering from schistosomiasis contaminate freshwater sources with their excreta containing parasite eggs which hatch in water.People become infected when larval forms of the parasite – released by freshwater snails – penetrate the skin during contact with infested water.In the body, the larvae develop into adult schistosomes. Adult worms live in the blood vessels where the females release eggs. Some of the eggs are passed out of the body in the faeces or urine to continue the parasite’s life-cycle. Others become trapped in body tissues, causing immune reactions and progressive damage to organs.


Schistosomiais is prevalent in tropical and sub-tropical areas, especially in poor communities without access to safe drinking water and adequate sanitation. It is estimated that at least 90% of those requiring treatment for schistosomiasis live in Africa.There are two major forms of schistosomiasis – intestinal and urogenital – caused by five main species of blood fluke (see table).

Table: Parasite species and geographical distribution of schistosomiasis

Species Geographical distribution

Intestinal schistosomiasis Schistosoma mansoni

Africa, the Middle East, the Caribbean, Brazil, Venezuela and Suriname

Schistosoma japonicum China, Indonesia, the Philippines

Schistosoma mekongi

Several districts of Cambodia and the Lao People’s Democratic Republic

Schistosoma guineensisand related S. intercalatum Rain forest areas of central Africa

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Species Geographical distribution

Urogenital schistosomiasis

Schistosoma haematobium

Africa, the Middle East, Corsica (France)

Table: Parasite species and geographical distribution of schistosomiasis

Schistosomiasis mostly affects poor and rural communities, particularly agricultural and fishing populations. Women doing domestic chores in infested water, such as washing clothes, are also at risk. Inadequate hygiene and contact with infected water make children especially vulnerable to infection.Migration to urban areas and population movements are introducing the disease to new areas. Increasing population size and the corresponding needs for power and water often result in development schemes, and environmental modifications facilitate transmission.With the rise in eco-tourism and travel “off the beaten track”, increasing numbers of tourists are contracting schistosomiasis. At times, tourists present with severe acute infection and unusual problems including paralysis.Urogenital schistosomiasis is also considered to be a risk factor for HIV infection, especially in women.


Symptoms of schistosomiasis are caused by the body’s reaction to the worms’ eggs.Intestinal schistosomiasis can result in abdominal pain, diarrhoea and blood in the stool. Liver enlargement is common in advanced cases, and is frequently associated with an accumulation of fluid in the peritoneal cavity and hypertension of the abdominal blood vessels. In such cases there may also be enlargement of the spleen.The classic sign of urogenital schistosomiasis is haematuria (blood in urine). Fibrosis of the bladder and ureter, and kidney damage are sometimes diagnosed in advanced cases. Bladder cancer is another possible complication in the later stages. In women, urogenital schistosomiasis may present with genital lesions, vaginal bleeding, pain during sexual intercourse and nodules in the vulva. In men, urogenital schistosomiasis can induce pathology of the seminal vesicles, prostate and other organs. This disease may also have other long-term irreversible consequences, including infertility.The economic and health effects of schistosomiasis are considerable and the disease disables more than it kills. In children, schistosomiasis can cause anaemia, stunting and a reduced ability to learn, although the effects are usually reversible with treatment. Chronic schistosomiasis may affect people’s ability to work and in some cases can result in death.1 The number deaths due to schistosomiasis is difficult to estimate because of hidden pathologies such as liver and kidney failure and bladder cancer. Estimates therefore vary widely between 20 000 and 200 0002deaths per year.


Schistosomiasis is diagnosed through the detection of parasite eggs in stool or urine specimens. Antibodies and/or antigens detected in blood or urine samples are also indications of infection.For urogenital schistosomiasis, a filtration technique using nylon, paper or polycarbonate filters is the standard diagnostic technique. Children with S. haematobium almost always have microscopic blood in their urine and this can be detected by chemical reagent strips.The eggs of intestinal schistosomiasis can be detected in faecal specimens through a technique using methylene blue-stained cellophane soaked in glycerine or glass slides, known as the Kato-Katz technique.

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For people living in non-endemic or low-transmission areas, serological and immunological tests may be useful in showing exposure to infection and the need for thorough examination, treatment and follow-up.

Prevention and control

The control of schistosomiasis is based on large-scale treatment of at-risk population groups, access to safe water, improved sanitation, hygiene education and snail control.The WHO strategy for schistosomiasis control focuses on reducing disease through periodic, targeted treatment with praziquantel. This involves regular treatment of all people of at-risk groups. In a few countries, where there is low transmission, the elimination of the disease should be aimed for.Groups targeted for treatment are:

school-aged children in endemic areas, adults considered to be at risk in endemic areas, and people with occupations involving

contact with infested water, such as fishermen, farmers, irrigation workers, and women whose domestic tasks bring them in contact with infested water,

entire communities living in highly endemic areas.

The frequency of treatment is determined by the prevalence of infection in school-age children. In high-transmission areas, treatment may have to be repeated every year for a number of years. Monitoring is essential to determine the impact of control interventions.The aim is to reduce disease: periodic treatment of at-risk populations will cure mild symptoms and prevent infected people from developing severe, late-stage chronic disease. However, a major limitation to schistosomiasis control has been the limited availability of praziquantel. Data for 2013 show that 13.1% of people requiring treatment were reached.Praziquantel is the recommended treatment against all forms of schistosomiasis. It is effective, safe and low-cost. Even though re-infection may occur after treatment, the risk of developing severe disease is diminished and even reversed when treatment is initiated and repeated in childhood.Schistosomiasis control has been successfully implemented over the past 40 years in several countries, including Brazil, Cambodia, China, Egypt, Mauritius and Saudi Arabia. There is evidence that schistosomiasis transmission was interrupted in Morocco. In Burkina Faso, Niger, Sierra Leone and Yemen, it has been possible to scale up schistosomiasis treatment to the national level and have an impact on the disease in a few years. An assessment of the status of transmission is being made in several countries.Over the past 10 years, there has been scale-up of treatment campaigns in a number of sub-Saharan countries, where most of those at risk live.WHO response

WHO’s work on schistosomiasis is part of an integrated approach to the control of neglected tropical diseases. Although medically diverse, neglected tropical diseases share features that allow them to persist in conditions of poverty, where they cluster and frequently overlap.WHO coordinates the strategy of preventive chemotherapy in consultation with collaborating centres and partners from academic and research institutions, the private sector, nongovernmental organizations, international development agencies and other United Nations organizations. WHO develops technical guidelines and tools for use by national control programmes.Working with partners and the private sector, WHO has advocated for increased access to praziquantel and resources for implementation. A significant amount of praziquantel, to treat more than 100 million children of the school age per year, has been pledged by the private sector and development partners.

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Sexually transmitted infections (STIs)

Fact sheet N°110Updated November 2013

Key facts

More than 1 million people acquire a sexually transmitted infection (STI) every day. Each year, an estimated 500 million people become ill with one of 4 STIs: chlamydia,

gonorrhoea, syphilis and trichomoniasis. More than 530 million people have the virus that causes genital herpes (HSV2).

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More than 290 million women have a human papillomavirus (HPV) infection. The majority of STIs are present without symptoms. Some STIs can increase the risk of HIV acquisition three-fold or more. STIs can have serious consequences beyond the immediate impact of the infection itself,

through mother-to-child transmission of infections and chronic diseases. Drug resistance, especially for gonorrhoea, is a major threat to reducing the impact of STIs


What are sexually transmitted infections and how are they transmitted?

STIs are caused by more than 30 different bacteria, viruses and parasites and are spread predominantly by sexual contact, including vaginal, anal and oral sex.Some STIs may be spread via skin-to-skin sexual contact. The organisms causing STIs can also be spread through non-sexual means such as blood products and tissue transfer. Many STIs—including chlamydia, gonorrhoea, hepatitis B, HIV, HPV, HSV2 and syphilis—can also be transmitted from mother to child during pregnancy and childbirth.A person can have an STI without having obvious symptoms of disease. Therefore, the term “sexually transmitted infection” is a broader term than “sexually transmitted disease” (STD). Common symptoms of STDs include vaginal discharge, urethral discharge in men, genital ulcers, and abdominal pain.Eight of the more than 30 pathogens known to be transmitted through sexual contact have been linked to the greatest incidence of illness. Of these 8 infections, 4 are currently curable: syphilis, gonorrhoea, chlamydia and trichomoniasis. The other four are viral infections and are incurable, but can be mitigated or modulated through treatment: hepatitis B, herpes, HIV, and HPV.

Scope of the problem

STIs have a profound impact on sexual and reproductive health worldwide, and rank among the top 5 disease categories for which adults seek health care.More than 1 million people acquire a sexually transmitted infection every day. Each year, an estimated 500 million people acquire one of four sexually transmitted infections: chlamydia, gonorrhoea, syphilis and trichomoniasis. More than 530 million people are living with HSV2. More than 290 million women have an HPV infection, one of the most common STIs.

Estimated new cases of curable sexually transmitted infections (gonorrhoea, chlamydia, syphilis and trichomoniasis) by WHO region, 2008

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STIs can have serious consequences beyond the immediate impact of the infection itself. Some STIs can increase the risk of HIV acquisition three-fold or more. Mother-to-child transmission of STIs can result in stillbirth, neonatal death, low-birth-weight

and prematurity, sepsis, pneumonia, neonatal conjunctivitis, and congenital deformities. Syphilis in pregnancy leads to approximately 305 000 fetal and neonatal deaths every year and leaves 215 000 infants at increased risk of dying from prematurity, low-birth-weight or congenital disease.

HPV infection causes 530 000 cases of cervical cancer and 275 000 cervical cancer deaths each year.

STIs such as gonorrhoea and chlamydia are major causes of pelvic inflammatory disease, adverse pregnancy outcomes and infertility.

Prevention of STIs

Counselling and behavioural approaches

Counselling and behavioural interventions offer primary prevention against STIs (including HIV), as well as against unintended pregnancies. These include:

comprehensive sexuality education, STI and HIV pre- and post-test counselling; safer sex/risk-reduction counselling, condom promotion; and interventions targeted at key and vulnerable populations, such as adolescents, sex workers,

men who have sex with men and people who inject drugs.

In addition, counselling can improve people’s ability to recognize the symptoms of STIs and increase the likelihood they will seek care or encourage a sexual partner to do so. Unfortunately, lack of public awareness, lack of training of health workers, and long-standing, widespread stigma around STIs remain barriers to greater and more effective use of these interventions.

Barrier methods

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When used correctly and consistently, condoms offer one of the most effective methods of protection against STIs, including HIV. Female condoms are effective and safe, but are not used as widely by national programmes as male condoms.

Diagnosis of STIs

Accurate diagnostic tests for STIs are widely used in high-income countries. These are especially useful for the diagnosis of asymptomatic infections. However, in low- and middle-income countries, diagnostic tests are largely unavailable. Where testing is available, it is often expensive and geographically inaccessible; and patients often need to wait a long time (or need to return) to receive results. As a result, follow up can be impeded and care or treatment can be incomplete.The only inexpensive, rapid blood test currently available for an STI is for syphilis. This test is already in use in some resource-limited settings. The test is accurate, can provide results in 15 to 20 minutes, and is easy to use with minimal training. Rapid syphilis tests have been shown to increase the number of pregnant women tested for syphilis. However, increased efforts are still needed in most low- and middle-income countries to ensure that all pregnant women receive a syphilis test.Several rapid tests for other STIs are under development and have the potential to improve STI diagnosis and treatment, especially in resource-limited settings.Treatment of STIs

Effective treatment is currently available for several STIs. Three bacterial STIs (chlamydia, gonorrhoea and syphilis) and one parasitic STI

(trichomoniasis) are generally curable with existing, effective single-dose regimens of antibiotics.

For herpes and HIV, the most effective medications available are antivirals that can modulate the course of the disease, though they cannot cure the disease.

For hepatitis B, immune system modulators (interferon) and antiviral medications can help to fight the virus and slow damage to the liver.

Resistance of STIs—in particular gonorrhoea—to antibiotics has increased rapidly in recent years and has reduced treatment options. The emergence of decreased susceptibility of gonorrhoea to the “last line” treatment option (oral and injectable cephalosporins) together with antimicrobial resistance already shown to penicillins, sulphonamides, tetracyclines, quinolones and macrolides make gonorrhoea a multidrug-resistant organism. Antimicrobial resistance for other STIs, though less common, also exists, making prevention and prompt treatment critical.

STI case managementLow- and middle-income countries rely on syndromic management, which is based on the identification of consistent groups of symptoms and easily recognized signs (syndromes) to guide treatment, without the use of laboratory tests. This approach, which often relies on clinical algorithms, allows health workers to diagnose a specific infection on the basis of observed syndromes.Syndromic management is simple, assures rapid, same-day treatment, and avoids expensive or unavailable diagnostic tests. However, this approach misses infections that do not demonstrate any syndromes - the majority of STIs globally.

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Vaccines and other biomedical interventions

Safe and highly effective vaccines are available for 2 STIs: hepatitis B and human papillomavirus (HPV). These vaccines have represented major advances in STI prevention. The vaccine against hepatitis B is included in infant immunization programmes in 93% of countries and has already prevented an estimated 1.3 million deaths from chronic liver disease and cancer.HPV vaccine is available as part of routine immunization programmes in 45 countries, most of them high- and middle-income. HPV vaccination could prevent the deaths of more than 4 million women over the next decade in low- and middle-income countries, where most cases of cervical cancer occur, if 70% vaccination coverage can be achieved.Research to develop vaccines against herpes and HIV is advanced, though no viable vaccine candidates for either infection have yet emerged. Research into vaccines for chlamydia, gonorrhoea, syphilis and trichomoniasis is in earlier stages of development.Other biomedical interventions to prevent some STIs include adult male circumcision and microbicides.

Male circumcision reduces the risk of heterosexually acquired HIV infection in men by approximately 60% and provides some protection against other STIs, such as herpes and HPV.

Tenofovir gel, a microbicide with the potential to allow women to actively avert HIV acquisition, reached “proof of concept” stage in clinical trials in 2010. Further clinical research to support regulatory approval of its safety and effectiveness is underway.

Current efforts to contain the spread of STIs are not sufficient

Behaviour change is complexDespite considerable efforts to identify simple interventions that can reduce risky sexual behaviour, behaviour change remains a complex challenge. Research has demonstrated the need to focus on carefully defined populations, consult extensively with the identified target populations, and involve them in design, implementation and evaluation.

Health services for screening and treatment of STIs remain weakPeople seeking screening and treatment for STIs face numerous problems. These include limited resources, stigmatization, poor quality of services, and little or no follow-up of sexual partners.

In many countries, STI services are provided separately and not available in primary health care, family planning and other routine health services.

In many settings, services are often unable to provide screening for asymptomatic infections, lacking trained personnel, laboratory capacity and adequate supplies of appropriate medicines.

Marginalized populations with the highest rates of STIs—such as sex workers, men who have sex with men, people who inject drugs, prison inmates, mobile populations and adolescents—often do not have access to adequate health services.

WHO response

WHO develops global norms and standards for STI treatment and prevention, strengthens systems for surveillance and monitoring, including those for drug-resistant gonorrhoea, and leads the setting of the global research agenda on STIs.Our work is guided by Millennium Development Goals 4, 5 and 6, the global strategy for the prevention and control of STIs adopted by the World Health Assembly in 2006 and the 2010 United

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Nations Secretary-General’s Global Strategy for Women's and Children's Health, which highlights the need for a comprehensive, integrated package of essential interventions, including information and services for the prevention of HIV and other sexually transmitted infections.WHO works with countries to:

Scale-up effective STI services including:o STI case management and counselingo syphilis testing and treatment, in particular for pregnant womeno hepatitis B and HPV vaccination.

Promote strategies to enhance STI-prevention impact including:o integrate STI services into existing health systemso promote sexual healtho measure the burden of STIso monitor and respond to STI antimicrobial resistance.

Support the development of new technologies for STI prevention such as:o point-of care diagnostic tests for STIso additional drugs for gonorrhoeao STI vaccines and other biomedical interventions.

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Soil-transmitted helminth infections

Fact sheet N°366Updated May 2015

Key facts

Soil-transmitted helminth infections are caused by different species of parasitic worms. They are transmitted by eggs present in human faeces, which contaminate the soil in areas

where sanitation is poor. Approximately 2 billion people are infected with soil-transmitted helminths worldwide. Infected children are physically, nutritionally and cognitively impaired. Control is based on:

I. periodical deworming to eliminate infecting wormsII. health education to prevent re-infection

III. improved sanitation to reduce soil contamination with infective eggs. Safe and effective medicines are available to control infection.

Soil-transmitted helminth infections are among the most common infections worldwide and affect the poorest and most deprived communities. They are transmitted by eggs present in human faeces which in turn contaminate soil in areas where sanitation is poor. The main species that infect people are the roundworm (Ascaris lumbricoides), the whipworm (Trichuris trichiura) and hookworms (Necator americanus and Ancylostoma duodenale).

Global distribution and prevalence

More than 1.5 billion people, or 24% of the world’s population, are infected with soil-transmitted helminth infections worldwide. Infections are widely distributed in tropical and subtropical areas, with the greatest numbers occurring in sub-Saharan Africa, the Americas, China and East Asia.Over 270 million preschool-age children and over 600 million school-age children live in areas where these parasites are intensively transmitted, and are in need of treatment and preventive interventions.


Soil-transmitted helminths are transmitted by eggs that are passed in the faeces of infected people. Adult worms live in the intestine where they produce thousands of eggs each day. In areas that lack adequate sanitation, these eggs contaminate the soil. This can happen in several ways: eggs that are attached to vegetables are ingested when the vegetables are not carefully cooked,

washed or peeled; eggs are ingested from contaminated water sources; eggs are ingested by children who play in the contaminated soil and then put their hands in their

mouths without washing them.

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In addition, hookworm eggs hatch in the soil, releasing larvae that mature into a form that can actively penetrate the skin. People become infected with hookworm primarily by walking barefoot on the contaminated soil.

There is no direct person-to-person transmission, or infection from fresh faeces, because eggs passed in faeces need about 3 weeks to mature in the soil before they become infective. Since these worms do not multiply in the human host, re-infection occurs only as a result of contact with infective stages in the environment.

Morbidity and symptomsMorbidity is related to the number of worms harboured. People with light infections usually have no symptoms. Heavier infections can cause a range of symptoms including intestinal manifestations (diarrhoea and abdominal pain), general malaise and weakness, and impaired cognitive and physical development. Hookworms cause chronic intestinal blood loss that can result in anaemia.

Nutritional effects

Soil-transmitted helminths impair the nutritional status of the people they infect in multiple ways. The worms feed on host tissues, including blood, which leads to a loss of iron and protein. The worms increase malabsorption of nutrients. In addition, roundworm may possibly compete

for vitamin A in the intestine. Some soil-transmitted helminths also cause loss of appetite and, therefore, a reduction of

nutritional intake and physical fitness. In particular, T. trichiura can cause diarrhoea and dysentery.

The nutritional impairment caused by soil-transmitted helminths is recognized to have a significant impact on growth and physical development.

WHO strategy for control

In 2001, delegates at the World Health Assembly unanimously endorsed a resolution (WHA54.19) urging endemic countries to start seriously tackling worms, specifically schistosomiasis and soil-transmitted helminths.The strategy for control of soil-transmitted helminth infections is to control morbidity through the periodic treatment of at-risk people living in endemic areas. People at risk are:

preschool children, school-age children, women of childbearing age (including pregnant women in the second and third

trimesters and breastfeeding women), adults in certain high-risk occupations such as tea-pickers or miners. WHO recommends periodic medicinal treatment (deworming) without previous

individual diagnosis to all at-risk people living in endemic areas. Treatment should be given once a year when the prevalence of soil-transmitted helminth infections in the community is over 20%, and twice a year when the prevalence of soil-transmitted helminth infections in the community is over 50%. This intervention reduces morbidity by reducing the worm burden. In addition:

health and hygiene education reduces transmission and reinfection by encouraging healthy behaviours; and

provision of adequate sanitation is also important but not always possible in resource-poor settings.

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Morbidity control aims to reduce intensity of infection and protect infected individuals from morbidity through periodic treatment of at-risk populations.

Periodic deworming can be easily integrated with child health days or supplementation programmes for preschool children, or integrated with school health programmes. In 2013, over 368 million schoolchildren were treated with anthelminthic medicines in endemic countries, corresponding to 42% of all children at risk.

Schools provide a particularly good entry point for deworming activities, as they allow the easy provision of the health and hygiene education component, such as promotion of handwashing and improved sanitation.

WHO recommended medicines

The WHO recommended medicines – albendazole (400 mg) and mebendazole (500 mg) – are effective, inexpensive and easy to administer by non-medical personnel (e.g. teachers). They have been through extensive safety testing and have been used in millions of people with few and minor side-effects.Both albendazole and mebendazole are donated to national ministries of health through WHO in all endemic countries for the treatment of all children of school age.

Global target

The global target is to eliminate morbidity due to soil-transmitted helminthiases in children by 2020. This will be obtained by regularly treating at least 75% of the children in endemic areas (an estimated 873 million).

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Fact sheet N°104Reviewed March 2015

Key facts

Tuberculosis (TB) is second only to HIV/AIDS as the greatest killer worldwide due to a single infectious agent.

In 2013, 9 million people fell ill with TB and 1.5 million died from the disease. Over 95% of TB deaths occur in low- and middle-income countries, and it is among the top 5

causes of death for women aged 15 to 44. In 2013, an estimated 550 000 children became ill with TB and An estimated 37 million lives were saved through TB diagnosis and treatment 80 000 HIV-

negative children died of TB. TB is a leading killer of HIV-positive people causing one fourth of all HIV-related deaths. Globally in 2013, an estimated 480 000 people developed multidrug resistant TB (MDR-TB). The estimated number of people falling ill with TB each year is declining, although very slowly,

which means that the world is on track to achieve the Millennium Development Goal to reverse the spread of TB by 2015.

The TB death rate dropped 45% between 1990 and 2013. between 2000 and 2013.

Tuberculosis (TB) is caused by bacteria (Mycobacterium tuberculosis) that most often affect the lungs. Tuberculosis is curable and preventable.TB is spread from person to person through the air. When people with lung TB cough, sneeze or spit, they propel the TB germs into the air. A person needs to inhale only a few of these germs to become infected.About one-third of the world's population has latent TB, which means people have been infected by TB bacteria but are not (yet) ill with the disease and cannot transmit the disease.People infected with TB bacteria have a lifetime risk of falling ill with TB of 10%. However persons with compromised immune systems, such as people living with HIV, malnutrition or diabetes, or people who use tobacco, have a much higher risk of falling ill.When a person develops active TB (disease), the symptoms (cough, fever, night sweats, weight loss etc.) may be mild for many months. This can lead to delays in seeking care, and results in transmission of the bacteria to others. People ill with TB can infect up to 10-15 other people through close contact over the course of a year. Without proper treatment up to two thirds of people ill with TB will die.

Who is most at risk?

Tuberculosis mostly affects young adults, in their most productive years. However, all age groups are at risk. Over 95% of cases and deaths are in developing countries.

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People who are infected with HIV are 26 to 31 times more likely to become sick with TB (see TB and HIV section). Risk of active TB is also greater in persons suffering from other conditions that impair the immune system.Over half a million children (0-14 years) fell ill with TB, and 80 000 HIV-negative children died from the disease in 2013.Tobacco use greatly increases the risk of TB disease and death. More than 20% of TB cases worldwide are attributable to smoking.

Global impact of TB

TB occurs in every part of the world. In 2013, the largest number of new TB cases occurred in the South-East Asia and Western Pacific Regions, accounting for 56% of new cases globally. However, Africa carried the greatest proportion of new cases per population with 280 cases per 100 000 population in 2013.In 2013, about 80% of reported TB cases occurred in 22 countries. Some countries are experiencing a major decline in cases, while in others the numbers are dropping very slowly. Brazil and China for example, are among the 22 countries that showed a sustained decline in TB cases over the past 20 years. In the last decade, the TB prevalence in Cambodia fell by almost 50%.

Symptoms and diagnosis

Common symptoms of active lung TB are cough with sputum and blood at times, chest pains, weakness, weight loss, fever and night sweats.Many countries still rely on a long-used method called sputum smear microscopy to diagnose TB. Trained laboratory technicians look at sputum samples under a microscope to see if TB bacteria are present. With three such tests, diagnosis can be made within a day, but this test does not detect numerous cases of less infectious forms of TB.Diagnosing MDR-TB (see Multidrug-resistant TB section below) and HIV-associated TB can be more complex. A new two-hour test that has proven highly effective in diagnosing TB and the presence of drug resistance is now being rolled-out in many countries.Tuberculosis is particularly difficult to diagnose in children.


TB is a treatable and curable disease. Active, drug-sensitive TB disease is treated with a standard six-month course of four antimicrobial drugs that are provided with information, supervision and support to the patient by a health worker or trained volunteer. Without such supervision and support, treatment adherence can be difficult and the disease can spread. The vast majority of TB cases can be cured when medicines are provided and taken properly.Between 2000 and 2013, an estimated 37 million lives were saved through TB diagnosis and treatment.

TB and HIV

At least one-third of people living with HIV worldwide in 2013 were infected with TB bacteria, although they did not become ill with active TB. People living with HIV are 26 to 31 times more likely to develop active TB disease than people without HIV.HIV and TB form a lethal combination, each speeding the other's progress. In 2013 about 360 000 people died of HIV-associated TB. Approximately 25% of deaths among HIV-positive people are due

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to TB. In 2013 there were an estimated 1.1 million new cases of TB amongst people who were HIV-positive, 78% of whom were living in Africa.WHO recommends a 12-component approach of collaborative TB-HIV activities, including actions for prevention and treatment of infection and disease, to reduce deaths.

Multidrug-resistant TB

Standard anti-TB drugs have been used for decades, and resistance to the medicines is widespread. Disease strains that are resistant to a single anti-TB drug have been documented in every country surveyed.Multidrug-resistant tuberculosis (MDR-TB) is a form of TB caused by bacteria that do not respond to, at least, isoniazid and rifampicin, the two most powerful, first-line (or standard) anti-TB drugs.The primary cause of MDR-TB is inappropriate treatment. Inappropriate or incorrect use of anti-TB drugs, or use of poor quality medicines, can all cause drug resistance.Disease caused by resistant bacteria fails to respond to conventional, first-line treatment. MDR-TB is treatable and curable by using second-line drugs. However second-line treatment options are limited and recommended medicines are not always available. The extensive chemotherapy required (up to two years of treatment) is more costly and can produce severe adverse drug reactions in patients.In some cases more severe drug resistance can develop. Extensively drug-resistant TB, XDR-TB, is a form of multi-drug resistant tuberculosis that responds to even fewer available medicines, including the most effective second-line anti-TB drugs.About 480 000 people developed MDR-TB in the world in 2013. More than half of these cases were in India, China and the Russian Federation. It is estimated that about 9.0% of MDR-TB cases had XDR-TB.

WHO response

WHO pursues six core functions in addressing TB.1. Provide global leadership on matters critical to TB.2. Develop evidence-based policies, strategies and standards for TB prevention, care and

control, and monitor their implementation.3. Provide technical support to Member States, catalyze change, and build sustainable capacity.4. Monitor the global TB situation, and measure progress in TB care, control, and financing.5. Shape the TB research agenda and stimulate the production, translation and dissemination

of valuable knowledge.6. Facilitate and engage in partnerships for TB action.

The WHO’s Stop TB Strategy, which is recommended for implementation by all countries and partners, aims to dramatically reduce TB by public and private actions at national and local levels such as :

1. pursue high-quality DOTS expansion and enhancement. DOTS is a five-point package to:a. secure political commitment, with adequate and sustained financingb. ensure early case detection, and diagnosis through quality-assured bacteriologyc. provide standardized treatment with supervision and patient supportd. ensure effective drug supply and management ande. monitor and evaluate performance and impact;2. address TB-HIV, MDR-TB, and the needs of poor and vulnerable populations;3. contribute to health system strengthening based on primary health care;4. engage all care providers;5. empower people with TB, and communities through partnership;

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6. enable and promote research.