Dengue

Virus

Dengue virus serotypes DENV-1 to DENV-4 (Flaviviridae)

Vector

Aedes aegypti and Aedes albopictus — day-biting, breeding in clean domestic water

Severe disease mechanism

Secondary infection with a different serotype and antibody-dependent enhancement

Other transmission

Vertical, transfusion and organ transplantation (rare)

• Estimated 100-400 million infections annually across more than 130 countries.
• Endemic across South and Southeast Asia, Latin America, the Caribbean, Africa and expanding with climate and urbanisation.
• Outbreaks follow monsoon and post-monsoon periods; case fatality falls below 1% with good supportive care and exceeds 10% without it.

• Residence or travel in endemic areas, prior infection with a different serotype, infancy and older age, pregnancy, obesity, diabetes, asthma, sickle cell disease, chronic kidney or heart disease.

1. 1Aedes bite inoculates virus into skin, where it replicates in dendritic cells.
2. 2Viraemia seeds monocytes and macrophages in lymphoid tissue, liver and bone marrow.
3. 3In secondary infection, non-neutralising cross-reactive antibodies enhance viral uptake via Fc receptors (antibody-dependent enhancement).
4. 4Massive cytokine release plus NS1-mediated glycocalyx injury increases capillary permeability.
5. 5Bone marrow suppression and immune-mediated platelet destruction produce thrombocytopenia and bleeding risk.

Normal physiology → mechanism → tissue change → clinical picture

1. 1Normal physiology: endothelial glycocalyx and tight junctions retain plasma proteins within vessels.
2. 2Mechanism: viral NS1 protein and cytokine release disrupt glycocalyx and endothelial junctions.
3. 3Tissue change: transient, reversible increase in vascular permeability with plasma leakage into pleural and peritoneal spaces.
4. 4Haematological effect: bone marrow suppression and immune platelet destruction cause thrombocytopenia; coagulopathy may follow.
5. 5Clinical manifestation: haemoconcentration, narrow pulse pressure, effusions and ascites, then hypovolaemic (dengue) shock.

• Abrupt high fever with severe headache and retro-orbital pain
• Severe myalgia and arthralgia ('break-bone')
• Nausea, vomiting, anorexia, metallic taste
• Macular then confluent blanching rash with islands of sparing during recovery
• Warning signs: persistent vomiting, severe abdominal pain, mucosal bleeding, lethargy or restlessness

• Flushed facies, conjunctival suffusion, positive tourniquet test
• Tender hepatomegaly, ascites, pleural effusion
• Narrow pulse pressure (≤ 20 mmHg), tachycardia with normal blood pressure (compensated shock)
• Cold clammy extremities, prolonged capillary refill, restlessness in decompensated shock
• Petechiae, gum bleeding, epistaxis; rarely major gastrointestinal haemorrhage

Typical

• Adult in an endemic city with 4 days of high fever, severe myalgia and retro-orbital pain, now afebrile with abdominal pain, platelets 60 × 10⁹/L and rising haematocrit.

Atypical

• Infant with only fever, irritability and poor feeding progressing rapidly to shock
• Expanded dengue syndrome: encephalitis, myocarditis or acute hepatitis without prominent leakage
• Elderly patient with minimal fever but early shock and pre-existing comorbidity
• Returning traveller with fever and rash misdiagnosed as viral exanthem
• Pregnancy with peripartum haemorrhage as the presenting problem

1. 1In an endemic or travel context, treat acute undifferentiated fever as possible dengue and record day of illness — timing drives everything.
2. 2Assess haemodynamics: pulse pressure, capillary refill, urine output, mental state.
3. 3Baseline FBC with haematocrit; repeat at least daily and more often in the critical phase.
4. 4Confirm: NS1 antigen or RT-PCR in days 1-5; IgM from day 5 onward.
5. 5Classify as dengue without warning signs (group A), with warning signs (group B) or severe dengue (group C).
6. 6Manage fluids to the group and phase; avoid over-hydration during recovery when leaked fluid returns.
7. 7Actively exclude co-endemic mimics: malaria, typhoid, leptospirosis, scrub typhus, chikungunya, COVID-19.

Probable dengue

Living in or travel to an endemic area with fever plus two of: nausea/vomiting, rash, aches, positive tourniquet test, leukopenia, any warning sign

Dengue with warning signs

Probable dengue plus any listed warning sign

Severe dengue

Severe plasma leakage (shock or respiratory distress from fluid accumulation), severe bleeding, or severe organ involvement (AST/ALT ≥ 1000, impaired consciousness, myocarditis, renal failure)

Initial

• FBC with haematocrit and platelets, NS1 antigen or RT-PCR (day 1-5), dengue IgM (day ≥ 5), liver enzymes, renal function, blood glucose.

Severity / monitoring

• Serial haematocrit and platelets (6-12 hourly in the critical phase), lactate, blood gas, coagulation screen, ultrasound for effusion and ascites.

Differential work-up

• Malaria smear or rapid test, blood cultures, leptospira and scrub typhus serology, urinalysis — mimics and co-infection.

Selected

• ECG and troponin if myocarditis suspected; cross-match if bleeding.

Malaria

Rule in: cyclical fever, splenomegaly, positive smear/RDT. Rule out: negative repeated smears with positive dengue NS1.

Typhoid

Rule in: stepwise fever, relative bradycardia, positive blood culture. Rule out: rapid defervescence with plasma leakage pattern.

Leptospirosis

Rule in: conjunctival suffusion with jaundice, calf tenderness, raised CK, water exposure. Rule out: normal renal and hepatic profile.

Scrub typhus

Rule in: eschar, regional lymphadenopathy, response to doxycycline. Rule out: no eschar with positive dengue serology.

Chikungunya

Rule in: severe persistent polyarthritis, less thrombocytopenia. Rule out: haemoconcentration and plasma leakage.

Sepsis / meningococcaemia

Rule in: focal source, purpura fulminans, neutrophilia. Rule out: leukopenia with dengue-positive testing.

Group A

Dengue without warning signs, tolerating oral fluids — home care with daily review

Group B

Warning signs or coexisting condition/social risk — admit for IV fluids and monitoring

Group C

Severe dengue — emergency fluid resuscitation and critical care

Group A — ambulatory

• Oral rehydration with electrolyte solution; paracetamol for fever and pain
• Strict avoidance of NSAIDs, aspirin, corticosteroids and intramuscular injections
• Written warning-sign advice and daily review until 48 h after defervescence

Group B — with warning signs

• Isotonic crystalloid 5-7 mL/kg/h for 1-2 h, then reduce to 3-5 then 2-3 mL/kg/h guided by haematocrit, urine output and haemodynamics
• Haematocrit and vitals every 4-6 hours; hourly urine output target 0.5 mL/kg/h
• Minimise fluid duration to 24-48 hours and stop as leakage resolves

Group C — severe dengue

• Compensated shock: 5-10 mL/kg crystalloid bolus over 1 h, reassess and taper
• Hypotensive shock: 20 mL/kg bolus over 15-30 min, then reassess; consider colloid if haematocrit stays high after crystalloid
• Falling haematocrit with ongoing instability suggests bleeding — transfuse packed red cells
• Platelet transfusion only for significant bleeding, not for a low count alone
• Intubation, inotropes and renal replacement therapy as required in critical care

Recovery and public health

• Watch for fluid overload during the recovery phase as extravasated fluid is reabsorbed — reduce or stop IV fluids and consider a diuretic.
• Vector control at home, mosquito nets and repellent to prevent onward transmission.

Paracetamol

Antipyretic and analgesic of choice; cap at 60 mg/kg/day and reduce with hepatitis

NSAIDs and aspirin

Contraindicated — increase bleeding risk and gastric injury

Corticosteroids

No proven benefit in dengue or dengue shock; avoid outside a trial

Isotonic crystalloid

Mainstay therapy; titrate to haemodynamics and haematocrit, not to a fixed regimen

Colloid

Consider in refractory shock with persistently high haematocrit after crystalloid

Platelet concentrate

Only for clinically significant bleeding or before an invasive procedure

Anticoagulants and antiplatelets

Usually withheld during significant thrombocytopenia; individualise with cardiology input

Critical phase

• Dengue shock syndrome, severe haemorrhage, respiratory distress from effusions and fluid overload.

Organ involvement

• Hepatitis with transaminases > 1000, acute kidney injury, myocarditis, encephalopathy and encephalitis, haemophagocytic syndrome.

Convalescent

• Prolonged fatigue, depression, alopecia, post-dengue arthralgia.

• With timely fluid management, case fatality is below 0.5-1%; untreated severe dengue mortality exceeds 10-20%.
• The critical phase lasts 24-48 hours — survival depends on judicious fluid titration through it.
• Both under-resuscitation (shock) and over-resuscitation (pulmonary oedema) cause avoidable death.
• Immunity to the infecting serotype is lifelong; cross-protection against others is only short-lived.

• Eliminate domestic breeding sites; community source reduction
• Repellents, long sleeves and screens — Aedes bites in daylight
• Vaccination where nationally recommended, with serostatus considerations
• Wolbachia and other vector-control programmes in endemic cities
• Early care-seeking education so warning signs are recognised at home

• Daily review during the febrile and critical phases for ambulatory patients
• Confirm platelet recovery and resolution of effusions before discharge from follow-up
• Discharge criteria: afebrile 48 h, improving appetite, stable haematocrit, rising platelets, adequate urine output, no respiratory distress
• Counsel that future infection with a different serotype carries higher severe-disease risk

Pregnancy

Higher risk of haemorrhage and preterm birth; peripartum management with obstetric and critical care input; vertical transmission possible

Infants and children

Rapid decompensation with subtle signs; weight-based fluids; watch for shock with normal blood pressure

Elderly

More comorbidity and atypical presentation; narrower safe fluid window

Obesity

Use ideal body weight for fluid calculation; higher severe disease risk

CKD / heart failure

Very high fluid-overload risk — smaller boluses with intensive reassessment

Anticoagulated patients

Review and usually hold anticoagulants and antiplatelets during thrombocytopenia

• WHO dengue guidelines for diagnosis, treatment, prevention and control (2024 update)
• National dengue programme guidance for your country

• No antiviral therapy has proven benefit; management remains meticulous fluid titration.
• Corticosteroids, IVIG and prophylactic platelet transfusion have not shown benefit in trials.
• Vaccine efficacy and safety vary substantially by prior serostatus — follow national policy.

• WHO dengue guidelines 2024 update (guideline, global).
• DrZep editorial summary, demo dataset v0.1.