Updated: 12/2/2018

Lassa Fever Virus

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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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