r. g. kar medical college and hospital, kolkata

R. G. Kar Medical College and Hospital, Kolkata.


Epidemiology, Prevention & Control of Dengue Fever /

DHF

Dr. Dilip Kumar Das


Dengue Syndrome: The Problem

• Most common arthropod-borne viral disease• Important emerging disease of the tropical

and sub-tropical regions• Predominantly in urban and semi-urban

areas• Globally 2.5 - 3 billion people live in areas

having active dengue transmission• Estimated 50 million dengue infections

occur every year


Geographical Distribution

• Africa • Southeast Asia (including India)• China • Middle East • Caribbean • Central and South America • Australia • South and Central Pacific

110 countries are endemic for dengue


P opu lation at r isk o f D F/ D H F in South - East A s ia R egion


Total population of the SEA Region = 1.5 billion

Total population at risk = 1.3 billion (87% )

DF/ DHF endemic countries of the SEAR

No report from Bhutan, DPR Korea and Nepal


Category of SEAR Countries

• Category A: Indonesia, Myanmar, Thailand • Category B: India, Bangladesh, Maldives, Sri Lanka

• Category C: Bhutan, Nepal

• Category D: DPR Korea


India, Bangladesh, Maldives &Sri Lanka : Category B Dengue

Status– DHF an emerging disease– Cyclical epidemics becoming more

frequent– Multiple virus serotypes circulating – Expanding geographically within the

country– Aedes aegypti principal epidemic

vector– Role of Aedes albopictus uncertain


Dengue Reporting States in India

• Andhra pradesh• Bihar• Chandigarh• Delhi• Goa• Gujarat• Haryana• Karnataka• Kerala

• Maharashtra• Sikkim• Punjab• Rajasthan• Tamil Nadu• Pondicherry• Uttar Pradesh• Dadra & Nagar Haveli• West Bengal


Dengue is spreading

• Certain states had dengue for long and are regularly reporting cases with cyclical peaks

• New states are reporting Dengue • Overall the toll of dengue is increasing

every year

• 30 states are reporting dengue• 450 million people are at risk


Agent: Dengue Virus

• Is an arbovirus - Genus flavivirus

• Composed of single-stranded RNA

• Has 4 serotypes (DEN-1, 2, 3, 4)

• All 4 serotypes are in circulation in India

• Transmitted by female Aedes mosquitoes

• Infection with one serotype confers lifelong immunity


Host • Infects humans and several species of

lower primates • Humans main reservoir of virus• Transmission cycle: ‘Man-Mosquito-Man’• All ages and both sexes are susceptible• Clinical features vary according to the

age of the patient• Deaths are more in children during DHF

outbreak


Vectors of Dengue • Aedes aegypti - principal

vector• Aedes albopictus- limited

role in transmission • Aedes aegypti wide

spread in tropical and sub-tropical countries

• Lives around human habitation

(Aedes aegypti mainly in domestic urban areas and Aedes albopictus in peri-domestic rural and near forest areas)


• Breeding habit: Vectors breed in several types of unused / discarded artificial containers

• Biting habit: Predominantly bites during the daytime and prefers for human blood

• Resting habit: Aedes aegypti is indoor rester and Aedes albopictus mainly outdoor rester

• Mosquito density fluctuates with rainfall and water storage practices


Transmission of Dengue Virusby Aedes aegypti

5Human #1

Illness

Viremia Viremia

Extrinsic incubation

period

DAYS0 8 12 16 20 24

28Human #2

Mosquito feeds /acquires virus

Mosquito refeeds /transmits virus

Intrinsicincubation

period

Illness


Replication and Transmission 1. Virus transmitted to human in mosquito saliva

2. Virus replicates in target organs

3. Virus infects white blood cells and lymphatic tissues 4. Virus released and

circulates in blood

3 4

1

2


Replication and Transmission

5. Second mosquito ingests virus with blood

6. Virus replicates in mosquito midgut and other organs, infects salivary glands

7. Virus replicates in salivary glands

6

7

5


Dengue Transmission Pattern

• Epidemic dengue - single viral strain introduced in a region

- sufficient susceptible hosts & adequate vectors: explosive transmission

• Hyper endemic dengue - continuous circulation of multiple virus serotype - large pool of susceptible hosts and competent

vectors constantly present - adults are generally immune - travelers are at more risk


Dengue – Clinical Presentation

• Asymptomatic• Symptomatic

▪ Undifferentiated fever▪ Dengue Fever (DF)▪ Dengue Haemorrhagic Fever (DHF)▪ Dengue Shock Syndrome (DSS)


Undifferentiated Fever

• Presents like other viral fevers • Infants, young children and some

adults are infected for the first time• Maculopapular rash may be present • Can not be differentiated from other

viral infections


Dengue Fever• Fever: An acute febrile illness of 2-7

days duration with two or more of the following manifestations

• Headache• Retro-orbital pain• Myalgia • Arthralgia • Rash• Hemorrhagic manifestations• Leucopenia


Dengue Haemorrhagic Fever

The following must all be present :• Fever, history of acute fever, lasting for 2-7 days,

occasionally biphasic. • Haemorrhagic tendencies, evidenced by at least one of

the following –– A positive tourniquet test– Petechiae, ecchymoses or purpura– Bleeding from the mucosa, gastrointestinal tract, injections

sites or other locations– Haematemesis or melaena

• Thrombocytopenia (100000 cells per mm3 or less)


DHF criteria…

• Evidence of plasma leakage due to increased vascular permeability, manifested by at least one of the following –– A rise in average haematocrit for age and sex >

20 % – A > 20 % drop in the haematocrit following volume

replacement treatment compared to baseline– Signs of plasma leakage (pleural effusion, ascites

and hypoproteinaemia)


Four Grades of DHF• Grade 1

– Fever and nonspecific constitutional symptoms– Positive tourniquet test is the only hemorrhagic

manifestation• Grade 2

– Grade 1 manifestations + spontaneous bleeding• Grade 3

– Circulatory failure manifested by rapid and weak pulse, narrow pulse pressure (< 20 mm Hg), hypotension, cold clammy skin and restlessness

• Grade 4– Profound shock (undetectable pulse and BP)


Dengue Shock Syndrome

• All the 4 criteria of DHF must be present, plus evidence of circulatory failure manifested by :

- Rapid and weak pulse, and - Narrow pulse pressure (< 20 mm Hg) or- Hypotension for age and - Cold clammy skin and restlessness.


Course of dengue illness: 3 phases

• Febrile phase• Critical phase• Recovery phase


Danger Signs in Dengue

• Minute spots on the skin suggesting bleeding within the skin

• Nose and/or gum bleeding• Abdominal pain or passage of black and

tanned stool• Refusal to take food or drink• Abnormal behaviour or drowsiness• Difficulty in breathing or cold hands and

feet• Reduced amount of urine being passed


Laboratory Diagnosis of DF/DHF

1.Isolation of the dengue virus from serum, plasma, leucocytes or autopsy samples

2.Demonstration of virus antigen or RNA: - Demonstration in autopsy tissue or in serum

samples - Detection of viral genomic sequences in autopsy

tissue, serum or CSF by PCR3.Serological Diagnosis: - Detection of IgM antibodies: 5 days after

symptoms - Detection of IgG antibodies: A fourfold or greater

increase in IgG titre in paired serum samples taken at an interval of 10-14 days confirms the diagnosis


Prevention and Control of Dengue/DHF

• No drug or vaccine available against dengue infection

• Vector control is the only method of choice

• Early detection and use of standard case management guidelines help in reducing mortality substantially

• Dengue fever/DHF surveillance


Dengue/DHF Surveillance

Surveillance is essential for:

Monitoring dengue situation in an areaEarly detection of an impending outbreakTimely preventive and control measures

Surveillance should include: - Epidemiological surveillance - Entomological (Vector)

surveillance - Laboratory based surveillance


Epidemiological Surveillance

• Use of standard case definitions• Organization of surveillance network - Routine reporting

- Sentinel reporting - Outbreak investigations

• Detecting early warning signals• Effective and efficient response

mechanism


Entomological (Vector) Surveillance

• Continuous process in endemic areas• Adult and Larval Surveillance: pre-monsoon,

monsoon and post-monsoon period to generate data for early warning signals for dengue outbreak

Entomological indices

- House Index - Container Index - Breteau Index


Laboratory Based Surveillance

• Isolation of the dengue virus • Demonstration of virus antigen • Serological Diagnosis - Detection of IgM antibodies - Detection of IgG antibodies


Early Warning Signals in Dengue/DHF Outbreaks

• Sudden increase in reporting of suspected cases with clustering in time and space

• Enhanced vector density as indicated through house index/container index/breteau index with reference to vector mosquito

• Detection of viral activity either in vector or man


Management of Dengue Case

• Early reporting of the suspected cases

• Management is primarily symptomatic & supportive


Management of DF

• Bed rest during acute febrile phase• Antipyretics (Paracetamol) or sponging • Analgesics or mild sedatives - No aspirin

should be given• Oral fluids and electrolyte therapy • No role of antibiotics or platelet transfusion• Should be monitored till afebrile and

platelet count and hematocrits are normal


Management of DHF

• Hospitalisation: Rise in haematocrit of > 20 %, platelet count

of 50000/ mm3 or less, spontaneous haemorrhage, signs and symptoms of shock, oliguria and circum-oral cyanosis

• Antipyretics • Plenty of oral fluids• Volume replacement by IV fluids • Serial haematocrit levels and frequent

assessment of vital signs e.g. urine output


Management of DSS

• Immediate administration of IV fluids to expand plasma volume

• Electrolyte levels and blood gases should be determined periodically and corrected

• Oxygen therapy in shock/hypotension• Blood transfusion in case with

significant haemorrhage• Fresh frozen plasma/concentrated

platelets in DIC


WHO guidelines for treatment

Patients divided into 3 broad groups

• Group A: Uncompleted disease• Group B: Patients for in-hospital

management • Group C: Requiring emergency treatment

and referral


Vector Control Measures

Personal Prophylactic Measures

• Use of mosquito repellent creams, liquids, coils, mats etc.

• Wearing of full sleeve shirts and full pants with socks

• Use of bed nets for sleeping infants and young children during day time


Biological Control• Use of larvivorous fishes in ornamental tanks,

fountains etc. • Use of biocides (Bacillus thuringiensis)

Chemical Control• Larvicide: Temephos (Abate)in permanent big

breeding containers • Adulticide: Pyrethrum spray- in indoor situations as

aerosol space spray

Malathion fogging or Ultra Low Volume (ULV) spray


Environmental Management & SourceReduction Methods

• Detection & elimination of mosquito breeding sources

• Management of roof tops, porticos and sunshades

• Proper covering of stored water • Reliable water supply • Observation of weekly dry day


Health Education for Community Participation and Inter- Sectoral Convergence

• At the household level• At the community level• At the institutional level


Legislative Measures

• Model civic byelaws• Building Construction Regulation Act• Environmental Health Act (HIA)• Health Impact Assessments

r. g. kar medical college and hospital, kolkata

Documents

kar medical college

dengue reporting states

dengue virusis

toll of dengue

human habitation aedes

category b dengue statusdhf

year30 states

spreadingcertain states