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Updated: Dec 2 2018

Lassa Fever Virus

  • 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
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