2. Epidemiology, Prevention & Control of Dengue Fever / DHF
Dr. Dilip Kumar Das

3. 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 billion people live in areas having active dengue transmission
Estimated 50 million dengue infections occur every year

4. 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

7. Category of SEAR Countries
Category A:
Indonesia, Myanmar, Thailand
Category B:
India, Bangladesh, Maldives, Sri Lanka
Category C:
Bhutan, Nepal
Category D:
DPR Korea

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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) 3

14. Mosquito density fluctuates with rainfall and water storage practices
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 3

15. Transmission of Dengue Virus by Aedes aegypti
Mosquito feeds /
Mosquito refeeds /
acquires virus
transmits virus
Extrinsic
incubation
period
Intrinsic
incubation
period
Viremia
Viremia
Illness
Illness 8 12 16 20 24 5 28
DAYS
Human #1
Human #2 5

16. 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 6

17. Replication and Transmission6 7 5
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 7

18. 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

19. Dengue – Clinical Presentation
Asymptomatic
Symptomatic
Undifferentiated fever
Dengue Fever (DF)
Dengue Haemorrhagic Fever (DHF)
Dengue Shock Syndrome (DSS)

20. 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

21. 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 18

22. 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 ( cells per mm3 or less)

23. 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)

24. 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) 23

25. Dengue Shock Syndrome - Rapid and weak pulse, and
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.

26. Course of dengue illness: 3 phases
Febrile phase
Critical phase
Recovery phase

27. 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 24

28. Laboratory Diagnosis of DF/DHF
Isolation of the dengue virus from serum, plasma, leucocytes or autopsy samples
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 PCR
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 days confirms the diagnosis

29. 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

30. Dengue/DHF Surveillance
Surveillance is essential for:
Monitoring dengue situation in an area
Early detection of an impending outbreak
Timely preventive and control measures
Surveillance should include:
- Epidemiological surveillance
- Entomological (Vector) surveillance
- Laboratory based surveillance

31. 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

32. 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

33. Laboratory Based Surveillance
Isolation of the dengue virus
Demonstration of virus antigen
Serological Diagnosis
- Detection of IgM antibodies
- Detection of IgG antibodies

34. 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

35. Management of Dengue Case
Early reporting of the suspected cases
Management is primarily symptomatic & supportive

36. 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

37. 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

38. 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

39. 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

40. 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

41. Biological Control Chemical Control
Use of chemical larvicides like abate in big breeding containers
Aerosol space spray 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

42. Environmental Management & Source
Reduction 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

43. Health Education for Community Participation and Inter- Sectoral Convergence
At the household level
At the community level
At the institutional level

44. Legislative Measures
Model civic byelaws
Building Construction Regulation Act
Environmental Health Act (HIA)
Health Impact Assessments