common human diseases

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COMMON HUMAN DISEASES

A disease is an abnormal condition of an organism thatimpairs bodily functions, associated with specific symptoms and

effects. It may be caused by external factors, such as infectious

disease , or it may be of autoimmune type.

In human beings, "disease" is often used more broadly to

refer to any condition that causes pain, dysfunction, distress,

social problems, and/or death to the person afflicted, or similar

problems for those in contact with the person. In this broader

sense, it sometimes includes injuries, disabilities, disorders,

syndromes, infections, isolated symptoms.

Classification:

Classification of diseases is often done based on the mode

of transmission,symptoms and disorders caused by it.Infectious

diseases are those which are clinically evident and result from

the presence of pathogenic microbial agents, includingviruses,bacteria, fungi, protozoa, multicellular parasites, and aberrant

proteins known as

prions.Non-infectious diseases are all other

diseases, including most forms of heart diseases, genetic diseases

and sexually transmitted disesae.The non-infectious diseases are

often caused because of the impairements in the human body such

as obesity,over-weightness and abnormal gene combination


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DISEASE

Infectious disease Non-infectiousdisease

Bacteria Fungi Virus Microbes

EPIDEMIC ENDEMIC PANDEMIC


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Human diseases which are found to be deadliest worldwide are

1) Swine influenza 2) SAARS 3) POLIOMYELITIS 4)

tuberculosis.

Swineinfluenza is an infection caused in humans from

pigs. As of 2009, the known SIV strains include influenza C and

the subtypes ofinfluenza A known asH1N1

,H1N2,H3N1,H3N2,

andH2N3.

Transmission of the virus from pigs to humans is not common and

does not always lead to human influenza, often resulting only in

the production ofantibodies in the blood. If transmission does

cause human influenza, it is called zoonotic swine flu. People with

regular exposure to pigs are at increased risk of swine flu

infectionSymptoms of zoonotic swine flu in humans are similar to

those of influenza and of influenza-like illness in general, namely

chillness, fever, sore throat ,muscle pains, severe headache,coughing, weakness and general discomfort.

Classification:

Of the three genera of influenza

viruses that cause human flu,influenza a is common in pigs andInfluenza c being rare.Influenza B has not been reported in pigs.

Within influenza A and influenza C, the strains found in pigs and

humans are largelydistinct

, although because of reassortment

there have been transfers of genes among strains crossing swine,

avian, and human species boundaries.

Influenza C viruses infect both humans

and pigs, but do not infect birds.Swine influenza is known to be

caused by influenza A type. Subtypes are H1N1

,H1N2,H2N3,H3N1, andH3N2. In pigs, three influenza A virus subtypes (H1N1,

H1N2, and H3N2) are the most common strains worldwide

Transmission:

Transmission between pigs

Influenza is quite common in pigs, with

about half of breeding pigs having been exposed to the virus

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worldwide.The main route of transmission is through direct

contact between infected and uninfected animals. These close

contacts are particularly common during animal transport.

Intensive farming may also increase therisk of transmission

, as the pigs are raised in very close proximity

to each other. The direct transfer of the virus probably occurs

either by pigs touching noses, or through dried mucus. Airborne

transmission through the aerosols produced by pigs coughing or

sneezing are also an important means of infection.This happens

within days of infection.

Transmission to humans People who work with poultry and

swine, especially people with intense exposures, are at increased

risk of zoonotic infection with influenza virus endemic in these

animals, and constitute a population of human hosts in which

zoonosis and reassortment can co-occur. Vaccination of these

persons is therfore an essentiality.

Interaction with avian H5N1 in pigs

Pigs are unusual as they can be infected with influenza

strains that usually infect three different species: pigs, birds and

humans. This makes pigs a host where influenza viruses might

exchange genes, producing new and dangerous strains

Main symptoms of swine flu :

In humans

Direct transmission of a swine flu virus from pigs to humans

is occasionally possible (called zoonotic swine flu). Generally this

disease occurs when agent is less immune or occurs along as

secondary infection.

In swine

In pigs influenza infection producesfever, lethargy, difficulty

in breathingand decreased appetite.In some cases the infection

can cause abortion. Although mortality is usually low (around 1

4%), the virus can produce weight loss and poor growth, causing

economic loss to farmers. Infected pigs can lose up to 12 pounds

of body weight over a 3 to 4 week period.

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Prevention:

Prevention of swine influenza has three components:prevention in swine, prevention of transmission to humans,

and prevention of its spread among humans.

In swine

Methods of preventing the spread of influenza among swine

include facility management, herd management, and vaccination.

Because much of the illness and death associated with swine flu

involves secondary infection.Facility management includes usingdisinfectants and ambient temperature to control virus in the

environment. The virus is unlikely to survive outside living cells for

more than two weeks, except in cold (but above freezing)

conditions, and it is readily inactivated by disinfectants.Herd

management includes not adding pigs carrying influenza to herds

that have not been exposed to the virus. The virus survives in

healthy carrier pigs for up to 3 months.Prevention mainly involves

culling of infected animals and isolation of infected humans.

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In humans

Prevention of pig to human transmission Although strains of swine influenza are usually not able to

infect humans, farmers and veterinarians areencouraged to use a face mask when dealing with

infected animals. The use of vaccines on swine to

prevent their infection is a major method of

limitingswine to human transmission.

Prevention of human to human transmission

Influenza spreads between humans through coughing or

sneezing and people touching something with the virus on it andthen touching their own nose or mouth. virus is not transmitted

through food.Thermal imaging, camera & screen, photography

are used for detecting pateints . Thermal imaging can detect

elevated body temperature, one of the signs of the virusN1H1

(Swine influenza )in airports.Social distancingis another tactic.

Severe Acute Respiratory Syndrome (SAARS)is arespiratory disease in humans which is caused by the SARS

coronavirus (SARS-CoV).But, SAARS is claimed tobe eradicated

as vaccine isHowever, SARS is not claimed to have been

eradicated (unlikesmallpox

), as it may still be present in itsnatural host reservoirs (animal populations) and may potentially

return into the human population in the future.

. SARS CORONAVIRUS:

Coronaviruses arepositive-strand

, envelopedRNA viruses

that are importantpathogens of mammals and birds. This group of

viruses cause enteric or respiratory tract infections in a variety ofanimals including humans, livestock and pets.

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Signs and symptoms

Initial symptoms are flu-like and may include:fever

,

myalgia, lethargy,gastrointestinalsymptoms, cough,sore throat

and other non-specific symptoms. The only symptom that is

common to all patients appears to be a fever above 38 C(100.4

F). Shortness of breath may occur later.

DIAGNOSIS:

A chest x-ray showing increased opacity in both lungs,

indicative of pneumonia, in a patient with SARS.

SARS may be suspected in a patient who has:

1)Any of the symptoms, including a fever of 38 C (100.4 F) or

higher, and

2) Contact with someone with a diagnosis of SARS within the last

10 days and travel to region where SAARS is in abundance.

Treatment

Antibiotics are ineffective as SARS is a viral disease.

Treatment of SARS so far has been largely supportive with

antipyretics, supplemental oxygen and ventilatory support as

needed.Suspected cases of SARS must be isolated, preferably in

negative pressure rooms, with complete barrier nursing

precautions taken for any necessary contact with these patients...

Currently , Corticosteroids and Ribavirin are the most common

drugs used for treatment of SARS

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Poliomyelitis, often called polio orinfantile paralysis, is an

acute viral infectious disease spread from person to person,

primarily via the fecal-oral route. Although around 90% of polio

infections cause no symptoms at all, affected individuals can

exhibit a range of symptoms if the virus enters the blood stream.

Different types of paralysis may occur, depending on the nerves

involved. Spinal polio is the most common form, characterized by

asymmetric paralysis that most often involves the legs. Bulbar

polio leads to weakness of muscles innervated by cranial nerves.

Bulbospinal polio is a combination of bulbar and spinal paralysis.

Poliovirus was identified in 1908 by Karl Landsteiner.By

1910, much of the world experienced a dramatic increase in polio

cases .This led to discover of a new vaccine for polio.

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POLIO LIFE CYCLE

Cause

Poliomyelitis is caused by infection with a member of the

genusEnterovirus known aspoliovirus (PV). This group ofRNA

viruses prefers to inhabit thegastrointestinal tract. There are three

types of serotypes and PV causes disease in humans

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alone..Individuals who are exposed to the virus, either through

infection or by immunization with polio vaccine, develop

immunity. Infection or vaccination with one serotype of poliovirus

does not provide immunity against the other serotypes, and full

immunity requires exposure to each serotype.

Transmission:

Poliomyelitis is highly contagious and spreads easily by

human-to-human contact. In endemic areas, wild polioviruses can

infect virtually the entire human population. Virus particles are

excreted in the faeces for several weeks following initial infectionin the host. The disease is transmitted primarily via the fecal-oral

route, by ingesting contaminated food or water. It is occasionally

transmitted via the oral-oral route, a mode especially visible in

areas with good sanitation and hygiene. . Although the virus can

cross the placenta during pregnancy, the fetus does not appear to

be affected by either maternal infection or polio vaccination.

Paralytic polio: Paralysis generally develops one to ten daysafter early symptoms begin, progresses for two to three days,

and is usually complete by the time the fever breaks.

Spinal polio: Spinal polio is the most common form ofparalytic poliomyelitis; it results from viral invasion of the

motor neurons. With the destruction of nerve cells, themuscles no longer receive signals from the brain or spinal

cord and finally completely paralyzed.Progression to

maximum paralysis is rapid (two to four days), and is

usually associated with fever and muscle pain.

Bulbar polio: Making up about 2% of cases of paralytic polio,bulbar polio occurs when poliovirus invades and destroys

nerves within the bulbar region of the brain stem. Thebulbar region is a white matter pathway that connects the

cerebral cortex to the brain stem producing symptoms of

encephalitis, and causes difficulty breathing, speaking and

swallowing

Bulbospinal Polio: Approximately 19% of all paralytic poliocases have both bulbar and spinal symptoms; this subtype is called

respiratory polio or bulbospinal polio. It can lead to paralysis of

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the arms and legs and may also affect swallowing and heart

functions.

Diagnosis

Paralytic poliomyelitis may be clinically suspected inindividuals experiencing acute onset of flaccid paralysis in one or

more limbs with decreased or absent tendon reflexes in the

affected limbs

PREVENTIONPassive immunization

In 1950, William Hammon purified the gamma globulincomponent of the blood plasma of polio survivors. He proposed

that the gamma globulin, which contained antibodies to poliovirus,

could be used to halt poliovirus infection, prevent disease, and

reduce the severity of disease in other patients who had contracted

polio..

Vaccine

Two types of vaccines are used throughout the world tocombat polio. Both types induce immunity to polio, efficiently

blocking person-to-person transmission of wild poliovirus, thereby

protecting both individual vaccine recipientsand the wider

community (so-called herd immunity).

The Salk vaccine, or inactivated poliovirus vaccine (IPV), is

based on poliovirus grown in a type of monkey kidney tissue

culture, which is chemically inactivated with formalin. After twodoses of IPV (given by injection), 90% or more of individuals

develop protective antibody to all three serotypes of poliovirus,

and at least 99% are immune to poliovirus following three doses .

Vaccine produces excellent immunity in the intestine (which helps

prevent infection with wild virus in areas where it is endemic.

Tuberculosis orTB (short for TubercleBacillus

) is a

common and often deadly infectious disease caused by

mycobacteria

, usually Mycobacterium tuberculosis in humans.

Tuberculosis usually attacks the lungs but can also affect other

parts of the body. It is spread through the air, when people who

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have the disease cough, sneeze, or spit. If left untreated, kills more

than 50% of its victims.

SIGNS AND SYMPTOMS

The classic symptoms are a chronic cough with blood-tinged

sputum,

fever

, night sweats

, andweight loss. Infection of other

organs causes a wide range of symptoms.Diagnosis: relies onradiology (commonly chest X-rays), a tuberculin skin test, blood

tests, as well as microscopic examination and microbiological

culture of bodily fluids.

TransmissionWhen people suffering from active pulmonary TB cough,

sneeze, speak, or spit, they expel infectious aerosol droplets 0.5 to

5 m in diameter.A single sneeze can release up to 40,000

droplets. Each one of these droplets may transmit the disease,

since the infectious dose of tuberculosis is very low and inhaling

less than ten bacteria may cause an infection. People with

prolonged, frequent, or intense contact are at particularly high

risk of becoming infected, with an estimated 22% infection rate. Aperson with active but untreated tuberculosis can infect 1015

other people per year. Transmission can only occur from people

with active TB.The probability of transmission from one person to

another depends upon the number of infectious droplets.If

someone does become infected, then it will take at least 21 days, or

three to four weeks, before the newly infected person can transmit

the disease to others. TB can also be transmitted by eating meat

infected with TB. Mycobacterium bovis causes TB in cattle.

Causes

The primary cause of TB, Mycobacterium tuberculosis, is

a small aerobic non-motile bacillus. High lipid content of this

pathogen accounts for many of its unique clinical characteristics.

It divides every 16 to 20 hours, an extremely slow rate compared

with other bacteria, which usually divide in less than an hour. In

nature, the bacterium can grow only within the cells of a host

organism, but M. tuberculosis can be culturedin vitro.Other

known pathogenic mycobacteria include Mycobacterium leprae

,

Mycobacterium avium and M. kansasii. The last two are part of

the nontuberculous mycobacteria (NTM) group.

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Prevention

TB prevention and control takes two parallel approaches.

In the first, people with TB and their contacts are identified and

then treated. Identification of infections often involves testing high-risk groups for TB. In the second approach, children are

vaccinated to protect them from TB. No vaccine is available that

provides reliable protection for adults. However, in tropical areas

where the levels of other species of mycobacteria are high,

exposure to nontuberculous mycobacteriagives some protection

against TB.

VaccinesSeveral new vaccines to prevent TB infection are being

developed. The first recombinant tuberculosis vaccine rBCG30

which can accelerate the disappearance of bacteria as well as

protect against re-infection in mice. A very promising TB vaccine,

MVA85A

, is currently inphase II trials and is based on a

genetically modifiedvaccinia virus.

Treatment

Treatment for TB uses antibiotics to kill the bacteria.

Effective TB treatment is difficult, due to the unusual structure and

chemical composition of the mycobacterial cell wall, which makes

many antibiotics ineffective and hinders the entry of drugs. TB

requires much longer periods of treatment (around 6 to 24

months) to entirely eliminate mycobacteria from the body. Latent

TB treatment usually uses a single antibiotic, while active TBdisease is best treated with combinations of several .

The above mentioned

diseases are controlled by the discovery of vaccines but the

second phase of these diseases is possible and it will be in a larger

epidemic scale.Therefore, there is a need for a healthy

environment for a healthy life.

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common human diseases

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