Tropical & Vector-Borne Critical Illness

• Acute undifferentiated fever may reflect malaria, dengue, scrub typhus, leptospirosis, enteric fever or bacterial sepsis. Use exposure, illness day, testing and repeated organ-function assessment; do not wait for a fixed day for the syndromes to diverge.
• Treat compatible lethal syndromes promptly while tests return: doxycycline for suspected scrub/rickettsial illness, IV penicillin/ceftriaxone for severe leptospirosis, and an appropriate β-lactam for bacterial sepsis. IV artesunate for confirmed/strongly suspected severe malaria; uncomplicated malaria uses oral treatment.
• Use disease-specific fluid targets: dengue needs the minimum maintaining perfusion, reduced/stopped as leakage resolves; severe malaria/scrub ARDS tolerates overload poorly. In leptospirosis/other AKI, start RRT for refractory overload, severe electrolyte/acidosis complications or another urgent indication, not oliguria alone.
• Eschar suggests scrub typhus; conjunctival suffusion/calf tenderness suggests leptospirosis. These clues are not definitive and may be absent. Correctly performed 20WBCT supports venom-induced coagulopathy where lab tests are unavailable; a normal test does not exclude envenoming.
• One positive test does not exclude coinfection. If malaria films are initially negative but suspicion is high, repeat q12–24 h for 3 sets; reassess discordant clinical progress. Consider TB with a compatible subacute/chronic syndrome, not duration alone.

Undifferentiated severe tropical fever

First tests: Full blood count, Sodium, potassium, bicarbonate, urea and creatinine, Liver biochemistry, Thick and thin malaria blood films.

Only if indicated: Blood cultures, Exposure- and illness-day-directed pathogen tests, PT/INR, aPTT and fibrinogen.

Repeat monitoring: Full blood count.

Dengue / severe dengue

First tests: Full blood count, Sodium, potassium, bicarbonate, urea and creatinine, Liver biochemistry, Dengue NAAT or NS1 antigen plus IgM.

Only if indicated: PT/INR, aPTT and fibrinogen, Lung/pleural ultrasound.

Repeat monitoring: Full blood count.

Severe malaria

First tests: Thick and thin malaria blood films, Blood glucose, Full blood count, Sodium, potassium, bicarbonate, urea and creatinine, Liver biochemistry.

Only if indicated: Blood lactate, Arterial blood gas.

Repeat monitoring: Thick and thin malaria blood films, Blood glucose.

Leptospirosis

First tests: Full blood count, Sodium, potassium, bicarbonate, urea and creatinine, Liver biochemistry, Leptospira PCR / serology.

Only if indicated: Chest X-ray, 12-lead ECG, PT/INR, aPTT and fibrinogen.

Repeat monitoring: Sodium, potassium, bicarbonate, urea and creatinine.

Scrub typhus

First tests: Full blood count, Sodium, potassium, bicarbonate, urea and creatinine, Liver biochemistry, Scrub typhus PCR / serology.

Only if indicated: Chest X-ray, Lumbar puncture and CSF studies.

Repeat monitoring: Sodium, potassium, bicarbonate, urea and creatinine.

Snakebite / envenoming

First tests: Serial envenoming assessment, Full blood count, PT/INR, aPTT and fibrinogen, Sodium, potassium, bicarbonate, urea and creatinine, Urinalysis and microscopy.

Only if indicated: 20-minute whole-blood clotting test, Creatine kinase, Arterial blood gas.

Repeat monitoring: PT/INR, aPTT and fibrinogen, Serial respiratory and neurological examination.

Suspected critical tuberculosis

First tests: WHO-recommended rapid molecular TB test, Chest X-ray.

Only if indicated: Mycobacterial culture and susceptibility testing, Lumbar puncture and CSF studies, HIV test, Sodium, potassium, bicarbonate, urea and creatinine.

Repeat monitoring: Clinical and organ-function monitoring.

• Acute Undifferentiated Fever in the Tropics: The First 6 Hours
• Severe Dengue: Managing Fluid by Phase
• Severe Malaria: Artesunate and the Complications
• Scrub Typhus, Leptospirosis and Other Treatable Zoonoses
• Snakebite: Clotting Test, Antivenom and Neurotoxicity
• Severe and Disseminated Tuberculosis in the ICU