Lassa fever is an acute viral haemorrhagic illness caused by Lassa virus (Arenavirus), endemic in West Africa (Nigeria, Sierra Leone, Liberia, Guinea).

Reservoir: multimammate rat (Mastomys natalensis). Transmission through rodent excreta, contaminated food and household items, and human-to-human via body fluids (nosocomial spread).
About 100,000 to 300,000 infections yearly with about 5,000 deaths; most infections are mild or asymptomatic (80%).
Case fatality 1% overall but 15 to 20% in hospitalised patients; higher in pregnancy (maternal and fetal loss above 80% in third trimester).
Sensorineural hearing loss in about 25 to 30% of survivors.

Gradual onset (6 to 21 days after exposure) of fever, malaise, sore throat, retrosternal pain, cough, vomiting, diarrhoea, and abdominal pain.
Severe disease: facial oedema, pleural effusion, conjunctival bleeding, mucosal bleeding, hypotension, shock, seizures, and encephalopathy.
Haemorrhage in only 15 to 20%.
Complications: acute kidney injury, myocarditis, pericarditis, and deafness during convalescence.

Ribavirin (most effective early, within 6 days of illness): IV 30 mg/kg (maximum 2 g) loading dose, then 16 mg/kg (maximum 1 g) every 6 hours for 4 days, then 8 mg/kg (maximum 500 mg) every 8 hours for 6 days; oral regimen where IV unavailable. Used in pregnancy (benefits outweigh risks).
Supportive: careful fluids (avoid overload due to capillary leak), electrolyte replacement, transfusion, vasopressors, mechanical ventilation, and renal replacement.
Treat malaria and bacterial co-infections empirically while awaiting results.
Infection prevention: PPE, isolation, safe handling of specimens, and contact tracing with 21-day follow up; ribavirin 500 mg every 6 hours for 7 days (post-exposure prophylaxis) for high risk exposure.
Audiology follow up and rehabilitation; rodent control and food storage education.

Lassa Fever

Overview

Clinical Features

Diagnosis

Management