Tropical and monsoon fevers

Approach to severe acute febrile illness

Reviewed Nov 2026·2 references
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In the monsoon, a febrile patient with thrombocytopenia, jaundice, AKI or ARDS could have malaria, dengue, leptospirosis, scrub typhus or enteric fever, alone or together. Send the core tests, then start empirical ceftriaxone plus doxycycline (or azithromycin), with artesunate if malaria is not yet excluded.

At the bedside

Timed steps
  1. 1

    Bedside

    Clues

    Eschar (groin, axilla, under breasts/waistband): scrub typhus. Conjunctival suffusion, calf tenderness, flood/sewage exposure: leptospirosis. Rash, retro-orbital pain, rising haematocrit: dengue. Travel/endemic zone, rigors: malaria. Step-ladder fever, relative bradycardia: enteric.

  2. 2

    Core panel

    Tests

    Peripheral smear + malaria RDT (repeat if negative), dengue NS1 (days 1-5)/IgM (after day 5), scrub typhus IgM ELISA, leptospira IgM, blood cultures ×2, CBC with haematocrit, LFT, creatinine, lactate, urine, CXR.

  3. 3

    Severe AFI

    Empirical

    Ceftriaxone 2 g IV daily + doxycycline 100 mg 12-hourly (azithromycin in pregnancy). Add IV artesunate if smear/RDT unavailable or pending in an endemic area.

  4. 4

    Common patterns

    Organ support

    ARDS (scrub, lepto, falciparum), AKI (lepto, falciparum), shock (dengue leakage vs septic), encephalopathy (cerebral malaria, scrub, JE), bleeding (dengue, lepto).

  5. 5

    48-72 h

    Review

    Narrow therapy once a diagnosis is confirmed; consider co-infection (up to 10-15% in some series) if not improving.

Distinguishing features of tropical fevers

DiseaseKey cluesTypical labsFirst-line ICU treatment
Falciparum malariaEndemic area, rigors, coma, jaundice, AKIParasitaemia, anaemia, low platelets, hypoglycaemiaIV artesunate
DengueRetro-orbital pain, rash, defervescence day 3-7 then shockRising haematocrit + falling platelets, leucopeniaFluids by phase; no antibiotics
LeptospirosisWater/sewage exposure, calf pain, conjunctival suffusionNon-oliguric hypokalaemic AKI, high bilirubin with modest ALT, high CPKPenicillin G or ceftriaxone
Scrub typhusEschar, lymphadenopathy, rural/bush exposureALT > AST, thrombocytopenia, ARDSDoxycycline ± azithromycin
Enteric feverStep-ladder fever, abdominal pain, relative bradycardiaNormal/low WBC, blood culture positive in week 1Ceftriaxone or azithromycin

Overlap is the rule; empirical dual cover is justified in severe disease until results return.

Red flag · call your senior now
Fever with altered sensorium, shock, SpO2 < 92% or bleeding: ICU-level care.
Pitfall
A single negative smear does not exclude malaria; repeat 12-24 hourly ×3.
Pitfall
Labelling all fever with thrombocytopenia as dengue and missing scrub typhus or malaria.
Pearl
Look for the eschar under clothing: painless, black, often in skin folds.

Calculators for this topic

qSOFA

Bedside prompt for poor outcome in suspected infection. Not a diagnostic test for sepsis.

SOFA score

Sequential Organ Failure Assessment: 0-4 per organ system, total 0-24. A rise of ≥ 2 from baseline with infection = sepsis.

References

  1. 1

    Singhi S, Chaudhary D, Varghese GM, et al. Tropical fevers: management guidelines. Indian J Crit Care Med. 2014;18(2):62-69

  2. 2

    Indian Council of Medical Research. Treatment Guidelines for Antimicrobial Use in Common Syndromes, 2nd edition. New Delhi: ICMR; 2019

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