Lassa fever is an acute viral hemorrhagic illness caused by the Lassa virus, an arenavirus endemic to West Africa.
The primary reservoir is the multimammate rodent Mastomys natalensis, and transmission to humans occurs mainly through contact with rodent urine, feces, or contaminated food.
Human-to-human transmission can also occur via direct contact with blood, bodily fluids, or contaminated medical equipment, posing a risk to healthcare workers.
Most infections are mild or asymptomatic, but about 20% progress to severe disease.
Early symptoms are nonspecific—fever, sore throat, headache, gastrointestinal symptoms, and general malaise.
Severe cases may develop hypotension, facial edema, respiratory distress, hemorrhage, multiorgan failure, and neurological complications.
Hospitalized patients have case fatality rates ranging from 15–30%, while overall mortality is estimated at 1–15%.
Lassa fever is a major public health concern in Nigeria, Sierra Leone, Guinea, Liberia, and neighboring countries, with an estimated 100,000–300,000 cases and 5,000 deaths annually.
Outbreaks are frequent, and imported cases have been reported in travelers.
Diagnosis relies on clinical suspicion in endemic areas and laboratory confirmation by PCR, antigen, or antibody tests.
Ribavirin is the only antiviral shown to improve outcomes, especially if given early.
A rVSVAG-LASV-GPC vaccine is being tested, but no approved vaccine exists.[6][3][8][9]