Dengue

Tropical / Viral

Patient + scenario modifiers

Patient

Clinical scenario / source

Annotations only — chart still shows the full chemistry of each drug.

1. Clinical Syndrome

Flavivirus illness from Aedes mosquito bite in tropical/subtropical regions. WHO 2009 classification: dengue without warning signs / dengue with warning signs / severe dengue.

Phases:

Febrile (days 1–3): high fever, severe myalgia, retro-orbital pain, headache, maculopapular rash.
Critical (days 3–7, at defervescence): plasma leakage → hemoconcentration, hypotension, hemorrhage. This is when severe dengue / shock develops.
Convalescent (days 7+): fluid reabsorption, can develop fluid overload + secondary rash.

Severe dengue = severe plasma leakage (shock, fluid accumulation with respiratory distress) OR severe bleeding OR severe organ impairment (AST/ALT >1000, impaired consciousness, heart / other organs).

Excludes: other arboviruses (Zika + chikungunya — same vector, overlapping presentation; co-infection possible), malaria (similar geography, do thick + thin smear), leptospirosis, typhoid (returning traveler ddx).

2. Pathogens

Consider the patient: Travel history (tropical Asia, Latin America, Caribbean, Africa, Pacific), prior dengue infection (secondary infection with different serotype → higher severe dengue risk via antibody-dependent enhancement), age (children + elderly at higher severe-dengue risk), pregnancy.

Consider the case: Day of illness (critical phase ~day 3–7 at defervescence), warning signs (abdominal pain, persistent vomiting, fluid accumulation, mucosal bleeding, lethargy, liver enlargement, ↑Hct with ↓platelets), severe dengue criteria.

Common

- Dengue Virus
  4 serotypes (DENV-1–4). Antibody-dependent enhancement with secondary heterologous infection → worse disease.

3. Empiric Therapy

Tier	First choice	Alternatives	Duration	Comments
Outpatient	Supportive care — · — · — Acetaminophen for fever + pain. AVOID NSAIDs and aspirin (bleeding risk + Reye in children). Oral hydration + monitoring.	—	Until defervescence + safe through critical phase (typically 5–7 days)	Dengue without warning signs in adults — outpatient with strict return precautions. Daily clinical assessment + Hct + platelets through critical phase. Warning signs (any) → admit.
Admitted to ward	IV crystalloid (NS or LR) per WHO protocol 5–7 mL/kg/h initial × 1–2 h → titrate by clinical response + Hct + UOP · — · IV Most patients respond to modest IV fluids. AVOID aggressive fluid loading — risk of fluid overload during reabsorption phase.	Platelet transfusion — · — · — Generally not indicated even with severe thrombocytopenia without active bleeding. Routine prophylactic transfusion does NOT prevent bleeding + may cause fluid overload. Transfuse only for significant bleeding.	Through critical phase (typically 24–48 h)	Dengue with warning signs. Monitor q1–2 h: vitals, capillary refill, peripheral perfusion, UOP, Hct (rises with leakage), platelets. Critical phase ~24–48 h at defervescence — leakage stops + reabsorption begins.
Admitted to ICU	Aggressive IV resuscitation per WHO 2009 severe dengue protocol 10–20 mL/kg crystalloid bolus over 1 h → reassess; consider colloid (5% albumin or 6% hetastarch) if no response · — · IV Vasopressors if persistent shock. Blood transfusion for significant hemorrhage (do NOT chase low Hct from leakage alone — that's hemoconcentration reversing).	—	Through severe phase (typically 24–48 h)	Severe dengue (shock, hemorrhage, organ failure). Mortality is supportive-care-quality-dependent (<1% with optimal care; up to 20% in resource-limited settings). NO specific antiviral. Avoid invasive procedures during thrombocytopenia. Monitor for fluid overload as critical phase resolves.

4. Directed Therapy

No specific antiviral. Cornerstones:

AVOID NSAIDs + aspirin — use acetaminophen only.
Daily CBC through critical phase — monitor Hct + platelets.
Daily assessment for warning signs (admit if any present).
Strict return precautions for outpatients: persistent vomiting, severe abdominal pain, mucosal bleeding, restlessness, dizziness, cold extremities → return urgently.
Hospital management for warning signs / severe dengue: WHO protocol IV crystalloid, frequent reassessment, judicious fluid titration.
Platelet transfusion only for active significant bleeding (not for thrombocytopenia alone, even profound).
Co-infection screening if symptoms severe / unclear: malaria (thick + thin smear), Zika, chikungunya, leptospirosis, typhoid.

Critical phase (defervescence ~day 3–7) is when severe dengue develops. Convalescent phase can cause fluid overload + secondary rash ("sea of red with islands of white").

Prevention:

Dengvaxia (CYD-TDV): only for seropositive ≥9 yo — risk of ADE in seronegatives. Limited use.
Qdenga (TAK-003): newer; approved for ages 4–60 across serostatus; broader use in endemic regions.
Vector control (DEET, permethrin, mosquito netting, indoor screens) remains primary prevention.

5. Monitoring

Resolution: defervescence + safe transit through critical phase (24–48 h post-defervescence) + clinical stability. Fluid balance through convalescence.

Severe dengue mortality: <1% with optimal supportive care; rises substantially in resource-limited settings.

Toxicity: avoid iatrogenic harm from over-resuscitation (pulmonary edema in convalescent phase) or platelet transfusion (fluid overload + transfusion-related lung injury).

Pearls

Returning traveler from tropics + fever within 14 days + thrombocytopenia + leukopenia → think dengue (plus malaria, Zika, chikungunya, typhoid, leptospirosis on the ddx). AVOID NSAIDs + aspirin — use acetaminophen. Critical phase at defervescence (counterintuitive — patient looks better but is actually entering the dangerous plasma-leakage window). IV fluid resuscitation is the management — judicious, not aggressive. Platelet transfusion for active bleeding only, NOT routine prophylaxis even with platelets <10K. Antibody-dependent enhancement with secondary heterologous serotype infection → worse disease (rationale for Dengvaxia seronegative restriction). Notifiable disease — report to local health department.