dengue fever, epidemiology, aedes, mosquito, vector competence, vector capacity, vector, treatment, case management, diagnosis, DHF, DSS, DF, DENV, arbovirus

1. EPIDEMIOLOGY OF DENGUE
DR MENAAL K.
JR- II
DEPARTMENT OF S. P. M
S. N. MEDICAL
COLLEGE, AGRA

2. The Epidemiological Triad
Agent-
Dengue Virus
Environment
& Vector
Host- Human,
Monkey

3. The Agent
• Arbovirus (ss RNA Virus)
• Genus Flavivirus
• Family Flaviviraede
• 4 serotypes- DENV 1, DENV 2, DENV 3& DENV 4
• Micro evolution: Many virulent genotypes are evolving to replace non
virulent genotypes
• Antigenic similarity but infection with one serotype does not provide
lifelong immunity for other serotypes (Cross Immunity lasts only a few
months),

4. DENV Has…
• A lipoprotein envelope
• 3 structural protein genes encoding: {CME}
• Nucleocapsid or core protein (C),
• Membrane- associated protein (M),
• Envelope protein (E), and
• 7 non-structural protein (NS) genes including, envelope
glycoprotein, NS 1
• NS 1 is of diagnostic and pathological importance.

7. The Host
• Infective Stage: 1 day before onset of fever to day 5
• Intrinsic Incubation Period: 4- 6 days
• High Risk Patients:
• Extremes of Age
• Pregnancy
• Any condition prone to heavy blood loss: Peptic ulcer disease;
menstruation; haemolytic anaemia; G- 6PD deficiencies;
thalassemia; patients on steroids, NSAIDS
• Any chronic condition: DM, HTn, Asthma, Cirrhosis, IHD, CRF

8. Remember… “Prior immune sensitization
worsens the disease scenario”
1st
Infectio
n with
DENV-
1
Asymptomatic/
Non specific
manifestations/
DF
2nd
Infection
with
DENV- 2, 3
or 4
DHF/
DSS/
Severe
Disease
Secondary Infection with DENV 2 or multiple infections with different
serotypes causes Severe Disease (DHF/ DSS)
DENV 1/ DENV 2 Sequence is the worst

9. Non neutralizing
Ab(s)
Mononuclear cells Cytokines, vasoacti
ve mediators
procoagulants
DIC
2nd

10. The Amplifiers
• Man
• Monkey

11. The Transmission Cycles
• Enzootic
• Monkey- Aedes- Monkey- Aedes
• Epizootic
• From Epidemic Cycle, DENV Crosses Over To Non Humans Via Bridge
Vectors, esply Macaca sinica In Sri Lanka
• Epidemic
• Human- Aedes- Human- Aedes

12. Huma
ns
Mosquito HumansExtrinsic I P
Mosquito
Intrinsic I P= 4- 6
days
(Range: 3- 14 days)
Extrinsic I P= 8- 10
days
Intrinsic I P

13. The Environment
• Tropical& Sub- tropical
• Urban, Peri urban; Rural
• Rapid Unplanned uncontrolled urbanization,
• Transportation: human movement and congregation
• Consumerism- Non biodegradable plastic, mismanaged solid waste
disposal
• Poor water storage and management
• Seasonal Pattern: Post Monsoon (But Perennial in Gujarat& South

14. WHEN YOU SEE THESE SIGHTS, KNOW FOR
SURE… YOU HAVE INVITED DENGUE… ITS
NEAR!!

17. An Epidemic, Endemic& Hyper Endemic
South- East Asia is divided into 3 Categories:
• Cat A: India, Bangladesh, Myanmar, Sri
Lanka, Indonesia, Thailand, Maldives
• Cat B: Bhutan, Nepal
• Cat C: DPR Korea

18. Global Warming
• 2 degree rise in temp-
• Shortens extrinsic IP- more infected mosquitos to further
spread DENV
• Enhances the life cycle of Aedes
• Shortens the size of the mosquito
• Rise in temp- mosquito bites more frequently due to
“dehydration”- further spreads DENV

19. The Vector
• Ae albopictus Eggs Survive Sub Freezing Temp
• Ae aegypti- Cosmo tropical species between latitudes 45°N and 35°S
• Vector Competency
• Vector Capacity
• Transovarial Spread
• Endophagic, Endophilic
• 16- 35 °C, 60- 80% Relative Humidity

20. Vector Competency
• High susceptibility to infecting virus
• Ability to replicate the virus
• Ability to transmit the virus to another host
• Both Ae. aegypti and Ae. albopictus carry high vectorial
competency for dengue viruses.

21. Vectorial Capacity: Depends on the
Environmental and Biological characteristics
of the Vector
Ae. aegypti
• Highly domesticated
• Strongly anthropophilic
• Nervous feeder (i.e. it bites more than
one host to complete one blood meal)
and
• Discordant species (i.e. it needs more
than one feed for the completion of the
gonotropic cycle)
• These habits epidemiologically result in
the generation of multiple cases and the
clustering of dengue cases in cities.
Ae. albopictus
• Feral
• Feeds on both humans and animals
• Aggressive feeder (i.e. it can complete its
blood meal in one go on one person)
• Concordant species (does not require a
second blood meal for the completion of
the gonotropic cycle)
• So, Ae. albopictus has poor vectorial
capacity.

22. Distribution of Aedes aegypti

23. Distribution of Aedes albopictus

24. DSS
DHF
DF
Asymptomatic
The Spectrum
2- 5% cases

26. DF/ DHF Grade Signs and Symptoms Laboratory
DF Fever with two of the following:
• Headache.
• Retro-orbital pain.
• Myalgia.
• Arthtralgia/bone pain.
• Rash.
• Haemorrhagic
manifestations.
• No evidence of plasma
leakage.
• Leucopenia (wbc ≤5000
cells/mm3).
• Thrombocytopenia (Platelet
count
<150 000 cells/mm3).
• Rising haematocrit (5% – 10%
).
• No evidence of plasma loss.
DHF I Fever and haemorrhagic manifestation
(positive tourniquet test) and evidence
of plasma leakage
Thrombocytopenia <100 000 cells/ mm3;
HCT rise ≥20%
DHF II As in Grade I plus spontaneous
bleeding.
Thrombocytopenia
<100 000 cells/mm3; HCT rise ≥20%.
DHF# III As in Grade I or II plus circulatory
failure
(weak pulse, narrow pulse pressure
(≤20 mmHg), hypotension,
restlessness).
Thrombocytopenia
<100 000 cells/mm3; HCT rise ≥20%.
DHF# IV As in Grade III plus profound shock with
undetectable BP and pulse
Thrombocytopenia
< 100 000 cells/mm3; HCT rise ≥20%.

27. Undifferentiated Fever
• Primary dengue infection
• May develop a simple fever indistinguishable from other viral
infections.
• Maculopapular or rubelliform rashes on face, neck and chest may
accompany the fever or may appear during defervescence (Day
3-5)

28. Dengue Fever
• Older children, adolescents and adults
• Acute (Sudden, sharp) rise in temperature (39°C- 40°C) for 5- 7 days
• Biphasic fever with severe headache, myalgia, arthralgia and bone pains
(break-bone fever), particularly in adults
• Rashes, flushed face, retro-orbital pain on eye movement or eye
pressure, photophobia
• Altered taste sensation, Anorexia, Sore throat, Dragging pain in inguinal region
• Leukopenia and thrombocytopenia- mild
• Occasionally, Haemorrhage such as gastrointestinal bleeding, hyper
menorrhea, massive epistaxis (DF with Hmrgh)

29. Sub
conjunctival
Haemorrhage Petechial
Haemorrhages Pale islands in
the red sea
Maculo-
papular Rash

30. Dengue Haemorrhagic Fever (DHF)
• Children less than 15 years of age in hyper endemic areas, in association with
repeated dengue infections (secondary dengue infection). Incidence of DHF in adults
is increasing
• Rarely DHF may occur in Primary infections with DENV-1 and DENV-3 as well as in
infants.
• Signs and symptoms similar to DF in the early febrile phase.
• Pale islands in red sea
• Positive tourniquet test (TT), petechiae on extremities, easy bruising and/or GI
haemorrhage

31. Warning Signs That May Occur At Or After
Defervescence (The Presence Of One Or More Of
These Signs Indicates The Need For Immediate
Medical Evaluation):
• Abdominal pain or tenderness
• Persistent vomiting
• Clinical fluid accumulation (i.e., Pleural effusion or ascites)
• Mucosal bleeding
• Lethargy or irritability, restlessness
• Oliguria
• Postural Hypotension
• Liver enlargement (≥2cm)
• Increases in haematocrit concurrent with rapid decrease in platelet count

32. Dengue Shock Syndrome (DSS)
• Hypovolemic shock due to plasma leakage
• Pleural effusion, Ascites (plasma leakage to pleural& peritoneal
cavities)
• Hypothermia- Cold clammy skin
• I C Bleeding
• Fulminant hepatic failure

33. DSS
• Is of short duration (12- 24 hrs), But can be fatal
• Patient is conscious till stage 4 of the shock (BP not recordable)
• Usually SBP falls late, but pulse pressure (SBP-DBP) deteriorates much
earlier ≤ 20 mmHg
• If prolonged, Shock causes metabolic acidosis and multi organ failure

35. Expanded Dengue Syndrome
• Severe organ involvement such as liver, kidneys, brain or heart
+/- evidence of plasma leakage
• May be associated with co- infections, comorbidities or
complications of prolonged shock

36. Depression,
Bradycardia
Asthenia
Circumoral cyanosis, weak
thread pulse

37. The Management
Prevention Vector control
Environmental modifications
Host modification- Vaccination
Treatment Early Diagnosis
Symptomatic Management

38. Clinical Diagnosis
• Sub conjunctival haemorrhage, easy bruising, Positive Tourniquet Test, Pulse Pressure≤ 20
mmHg
Lab Diagnosis
• PCV - the earliest feature of DHF
• Platelet
• TLC
• Serum Albumin
• LFT- AST
• Chest X ray (Lateral Decubitus): Right Pleural Effusion
• USG Abdomen: GB wall edema, Liver enlargement, Ascites; Splenomegaly in Infants only
Serology
• IgG 4- fold rise in titre (by haemagglutination inhibition test)
• IgM against NS- 1 (ELISA)
RT PCR or Viral Isolation or Viral Ag Detection by IHC, IF or ELISA
Early Diagnosis

41. Case Management
• During an epidemic, every hospital should have Dengue Triage Facility.
• High risk Cases should be screened in the special Dengue OPD, on the basis of
history of any bleeding episodes, presence of warning signs, spread of dengue
infection in the neighbourhood along with fever.
• All these cases should be lab investigated
• On confirmation they need to be observed and managed in a Special Dengue
Wards

43. Management of Dengue Cases
• Fluid Intake- Oral or IV.
• ORS and fruit juices Better than water
• Antipyretics- PCM.
• AVOID ASPIRIN (May cause Rye’s Syndrome); other NSAIDS, e.g.
IBUPROFEN (these may cause gastric bleeding)
• Monitor for warning signs
• Daily check PCV from Day 3 of fever till Day 2 after fever

44. Indications of Red Cell Transfusion
1. Loss of blood (Overt blood loss)- 10% or more of total blood
volume- give whole blood
2. Refractory shock despite adequate fluid administration and
declining PCV
3. Replacement Volume should be 10ml/ kg
4. Coagulogram should be done

45. Indication of Platelet Transfusion
• There is no need to give prophylactic platelets even at
<20, 000/ cumm
• Prophylactic platelets should be given at levels <10, 000/
cumm
• Prolonged shock with coagulopathy and abnormal
coagulogram
• If systemic massive bleeding, platelet transfusion may be

46. Criteria for Discharge of the Patient
• Absence of fever for >24hr (without the use of antipyretics)
• Return of appetite
• Good urine output
• Visible clinical improvement
• Minimum 2- 3 days after recovery from shock
• No respiratory distress (due to pleural effusion or ascites)
• Platelet count > 50, 000/ cumm