Snapshot A 57-year-old woman presents to a clinic in Liberia for high fevers, nausea, and vomiting. She also reports having generalized myalgias and headaches. She works at a restaurant and has seen some rats and mice when she has been cleaning up. She has been having symptoms for about a week now and have increased in severity. On physical exam, she has a maculopapular rash over her chest and back and conjunctival injection. She is admitted to the hospital for further management. Introduction Classification Lassa fever virus an enveloped, circular, single-stranded, both positive and negative-sense RNA virus with a helical capsid an arenavirus causes Lassa fever encephalitis rodents (Mastomys natalensis species) are reservoirs transmission via direct contact with rodents or infected humans Epidemiology incidence endemic in West Africa risk factors exposure to rodents or rodent excretions travel to endemic areas Pathogenesis the virus infects dendritic cells and macrophages and subsequently disseminates throughout the body replication in endothelial cells cause capillary leak and hemorrhage Prevention rodent avoidance Prognosis most are asymptomatic if symptomatic, symptoms present 1-3 weeks after exposure with flu-like illness less than a third of patients have hemorrhagic manifestations mortality rate is ~1% Presentation Symptoms malaise headache nausea and vomiting diarrhea Physical exam high-grade fever generalized maculopapular rash appears ~1 week after fever hemorrhage from eyes, nose, or mouth appears ~ 1 week after initial symptom onset Studies Labs detection of Lassa virus-specific antibodies with enzyme-linked immunosorbent serologic assays (ELISA) detection of RNA with reverse-transcriptase polymerase chain reaction (RT-PCR) Making the diagnosis based on clinical presentation and laboratory studies Differential Ebola virus infection distinguishing factors also presents with a flu-like illness with high fever, myalgias, and headaches however, Ebola virus infection presents with a petechial rash rather than maculopapular rash can also have hematemesis and melena Treatment Management approach the mainstay of treatment is supportive care Conservative supportive care indication all patients modalities hemodynamic support intravenous hydration blood transfusions Medical ribavirin indication if patients present early in the disease course outcomes may be effective Complications Sensorineural hearing loss occurs in 30% of patients results due to damage to outer hair cells of the cochlea from circulating Lassa virus antibodies