Dengue Fever — Overview, Symptoms, Diagnosis, OPD Protocol & Differentials

1. Overview

2. Clinical Course & Symptoms

• Abrupt high fever, facial flushing, severe headache, retro-orbital pain
• Myalgia, arthralgia ("break-bone fever"), bone pain
• Anorexia, nausea/vomiting, epigastric discomfort, right hypochondrial tenderness
• Facial erythema, injected oropharynx
• Maculopapular/rubelliform rash (may appear early or late)
• Minor bleeding: petechiae, positive tourniquet test (≥10 petechiae/inch² positive; ≥20 typical in DHF)

• Temperature drops to ≤37.5-38°C while capillary permeability rises
• Progressive leukopenia followed by rapid platelet fall precedes plasma leakage
• Lasts 24-48 hours - this is when warning signs and shock develop
• Hemoconcentration (rising hematocrit) and thrombocytopenia are the hallmark lab findings distinguishing severe disease

• Gradual reabsorption of extravasated fluid, hemodynamic stabilization over 2-3 days
• May see a confluent "isles of white in a sea of red" rash and marked bradycardia

3. WHO (2009) Classification & Diagnostic Criteria

• Abdominal pain or tenderness
• Persistent vomiting
• Clinical fluid accumulation (ascites, pleural effusion)
• Mucosal bleeding
• Lethargy, restlessness
• Liver enlargement >2 cm
• Laboratory: rising hematocrit with rapid platelet drop

• Severe plasma leakage → shock (dengue shock syndrome) or fluid accumulation with respiratory distress
• Severe bleeding (clinician-assessed)
• Severe organ involvement: AST/ALT ≥1000 IU/L, impaired consciousness, cardiac or other organ failure (Less common: myocarditis, pancreatitis, hepatitis, hemophagocytic lymphohistiocytosis, encephalitis/ADEM)

• NS1 antigen ELISA/rapid test - positive from day 1 of fever (early infection)
• IgM capture ELISA - reliable after day 5 of illness
• RT-PCR - detects viral RNA during the viremic phase (best in first few days)
• Serology less reliable if patient previously received a dengue vaccine
• Supportive labs: leukopenia, thrombocytopenia, rising hematocrit (hemoconcentration), elevated transaminases

4. OPD (Outpatient / "Group A") Treatment Protocol

1. Hydration: Encourage oral rehydration - oral fluids/ORS; target urine output ≥0.5 ml/kg/hr (adults) or ≥1 ml/kg/hr (children)
2. Antipyretic/analgesic: Paracetamol only (max 4 g/day in adults) for fever and pain
3. Strictly avoid: NSAIDs (ibuprofen, diclofenac) and aspirin - risk of bleeding and Reye syndrome; also avoid unnecessary IM injections
4. Serial monitoring: Daily review of clinical status; CBC (hematocrit + platelet count) on day 3 of fever and then daily until 24-48 hours after defervescence (afebrile)
5. Patient/caregiver education on warning signs - instruct to return immediately if any of the following develop:
   • Severe abdominal pain, persistent vomiting
   • Bleeding (gums, nose, black stools, heavy menses)
   • Lethargy, restlessness, or irritability
   • Cold, clammy skin; difficulty breathing
   • No urine output for >4-6 hours
6. Referral/upgrade criteria: leukopenia (WBC ≤5000/mm³), rising hematocrit with falling platelets, pregnancy, infancy, obesity, diabetes, renal failure, or other comorbidities warrant closer observation/hospitalization even without overt warning signs (Group B1).
7. No specific antiviral exists - management is entirely supportive.

5. Differential Diagnosis

• Other arboviral infections: Zika, chikungunya, yellow fever
• Malaria
• Rickettsial infections (scrub typhus, spotted fever)
• Leptospirosis
• Other viral hemorrhagic fevers: Ebola, Marburg, bunyavirus infections
• Measles (important in returned travelers with fever + rash, since endemic overlap with dengue is common)
• Other considerations in practice: enteric fever (typhoid), influenza, COVID-19, acute HIV seroconversion, and other causes of thrombocytopenic febrile illness

Key Distinguishing Point