Dengue Fever — WHO Classification & Management
Dengue is the fastest-spreading mosquito-borne viral disease in India, with 1-3 lakh cases annually and outbreak-driven peaks during monsoon and post-monsoon seasons. The WHO 2009 classification replaced the older DHF/DSS system and guides fluid therapy — the only specific treatment for dengue. With proper case management, case fatality can be kept below 0.5%.
Dengue is caused by dengue virus (4 serotypes: DEN-1, DEN-2, DEN-3, DEN-4), transmitted by Aedes aegypti and Aedes albopictus mosquitoes. Day-biting mosquitoes that breed in clean stagnant water — flower pots, coolers, discarded tyres, construction sites. After infection with one serotype, lifelong immunity to that serotype but transient cross-immunity to others — second infection with different serotype carries higher risk of severe dengue (antibody-dependent enhancement).
Clinical features: Sudden high fever (39-40°C) lasting 2-7 days, retro-orbital pain, severe headache (especially frontal), myalgia, arthralgia (break-bone fever), maculopapular rash (sparing palms and soles), mild bleeding manifestations (petechiae, gum bleed, epistaxis, menorrhagia). Leukopenia, thrombocytopenia, and rising haematocrit are characteristic laboratory findings.
- NS1 antigen ELISA: Detects viral antigen. Positive from Day 1-5 of fever. Sensitivity > 90% in first 3 days. Most useful early test.
- IgM antibody ELISA: Detects anti-dengue IgM. Positive from Day 5 of fever, persists for 2-3 months. Indicates recent infection.
- IgG antibody ELISA: Detects anti-dengue IgG. Persists for life. IgG > IgM ratio or 4-fold rise in paired sera indicates secondary infection.
- RT-PCR: Detects viral RNA. Most accurate in first 5 days. Available at district level — used for serotyping during outbreaks.
- CBC: Leukopenia (WBC < 5000), thrombocytopenia (platelets < 1 lakh), rising haematocrit (> 20% increase from baseline indicates plasma leakage)
- LFT: Mild transaminitis (AST > ALT), hypoalbuminaemia
- USG abdomen: Gallbladder wall thickening, ascites, pleural effusion — markers of plasma leakage
| Category | Criteria | Setting |
|---|---|---|
| Dengue without warning signs | Fever + 2 of: nausea/vomiting, rash, aches/pains, tourniquet test positive, leukopenia | Home with oral fluids, follow-up |
| Dengue with warning signs | Above + any warning sign (see below) | Hospital admission, IV fluids |
| Severe dengue | Severe plasma leakage (shock, fluid accumulation with respiratory distress), severe bleeding, severe organ impairment (liver, CNS, heart, kidney) | ICU, aggressive resuscitation |
- Abdominal pain or tenderness
- Persistent vomiting (≥ 3 episodes in 24 hours)
- Clinical fluid accumulation (ascites, pleural effusion)
- Mucosal bleed (gum, nose, GI, vaginal)
- Lethargy, restlessness
- Hepatomegaly (> 2 cm)
- Rapid increase in haematocrit with drop in platelets
Critical phase: 24-48 hours around defervescence (when fever drops). This is when plasma leakage and shock typically occur. Monitor closely — vital signs every 1-4 hours, haematocrit every 6-12 hours, platelet count daily.
Dengue without warning signs (Plan A): Home management
- Oral fluids — 2-3 litres/day (water, ORS, coconut water, lemon water, soup)
- Paracetamol for fever (max 60 mg/kg/day in children, 4 g/day in adults). Avoid NSAIDs (aspirin, ibuprofen, diclofenac) — bleeding risk
- Tepid sponging for high fever
- Monitor for warning signs — return immediately if any develop
- Follow-up daily for platelet and haematocrit check
Dengue with warning signs (Plan B): Hospital admission
- Isotonic crystalloid (Normal Saline 0.9% or Ringer's Lactate) at 5-7 mL/kg/hour for 1-2 hours, then reduce to 3-5 mL/kg/hr based on clinical response
- Reassess every 1-2 hours — vital signs, haematocrit, urine output (target 0.5 mL/kg/hr)
- Continue IV fluids for 24-48 hours (critical phase)
- Switch to oral fluids once patient stable
Severe dengue (Plan C): ICU, emergency resuscitation
- Dengue shock: 10-20 mL/kg isotonic crystalloid bolus over 1 hour, repeat if needed. If shock persists, add colloid (albumin, starch) — prefer colloid if haematocrit still rising
- Once haematocrit stabilises and vital signs improve, reduce to 5-7 mL/kg/hr, then taper
- Blood transfusion if significant bleeding with haemodynamic instability
- Platelet transfusion: ONLY if active bleeding with platelets < 50,000 OR prophylactically if platelets < 10,000 OR if procedural/surgical indication. Routine prophylactic platelet transfusion is NOT recommended.
- Oxygen, vasopressors if refractory shock, dialysis for AKI
Dengue management is fluid management — there is no antiviral, only supportive care. For UPSC CMS aspirants, WHO 2009 classification, warning signs, and the three fluid management plans are extremely high-yield topics.