Dengue epidemiology& case management

EPIDEMIOLOGY OF DENGUE

DR MENAAL K.JR- II

DEPARTMENT OF S. P. MS. N. MEDICAL COLLEGE, AGRA

The Epidemiological Triad

Agent- Dengue

Virus

Environment &

Vector

Host- Human,Monkey

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),

• …Instead prior immune sensitization worsens the disease scenario

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.

• It is associated with viral haemagglutination and neutralization activity.

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

Remember… “Prior immune sensitization worsens the disease

scenario”

1st Infecti

on with

DENV- 1

Asymptomatic/ Non specific manifestation

s/ 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

Non neutralizing Ab(s)

Mononuclear cells

Cytokines, vasoactive mediators

procoagulants

DIC

2nd Infection

The Amplifiers

• Man

• Monkey

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

Humans

Mosquito

HumansExtrinsic I P

Mosquito

Intrinsic I P= 4- 6 days(Range: 3- 14 days)

Extrinsic I P= 8- 10 days

Intrinsic I P

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 India)

WHEN YOU SEE THESE SIGHTS, KNOW FOR SURE… YOU HAVE INVITED DENGUE… ITS

NEAR!!

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

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

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

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.

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.

Distribution of Aedes aegypti

Distribution of Aedes albopictus

DSSDHF

DF

Asymptomatic

The Spectrum2- 5% cases

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%.

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)

• URTI and GI symptoms are common

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)

Sub conjunctival Haemorrhag

ePetechial

Haemorrhages

Pale islands in the red

sea

Maculo- papular

Rash

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

• Abnormal haemostasis and plasma leakage are the main pathophysiological hallmarks of DHF

• Thrombocytopenia and rising haematocrit/haemo concentration before the subsidence of fever/ onset of shock.

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

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

• Optimal fluid management is important- Avoid over

hydration

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

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

Depression,BradycardiaAsthenia

Circumoral cyanosis, weak thread pulse

The Management

Prevention

Vector controlEnvironmental modificationsHost modification- Vaccination

Treatment

Early Diagnosis

Symptomatic Management

Clinical Diagnosis• Sub conjunctival haemorrhage, easy bruising, Positive Tourniquet Test, Pulse

Pressure≤ 20 mmHgLab 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 onlySerology• 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

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

• All dengue cases must be notified as soon as possible

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

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

5. If fluid overload happens, give packed cells

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 needed in addition to red cell transfusion

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