Lassa fever


  • RNA virus of arenaviridae family
  • Endemic to parts of West Africa
    • 100,000-300,000 infections every year
  • Animal vector: Multimammate rat (Mastomys natalensis)
  • A type of viral hemorrhagic fever


  • Infected Multimammate rats shed virus in urine and droppings
  • Inhalation, ingestion, or direct contact of excrement or soiled food
  • Direct contact with bodily fluids of infected human

Clinical Features

  • Incubation period: 1-3 weeks
  • 80% of infections are mild
    • Undiagnosed or low fever, malaise, headache
  • 20% of infections are severe
    • vomiting, diarrhea, respiratory distress, facial swelling, body pain, hemorrhage, shock
    • death within 2 weeks due to multi-system organ failure
  • Occasional neurologic symptoms: hearing loss, tremors, encephalitis

Differential Diagnosis

Fever in traveler


  • IgM or IgG ELISA or RT-PCR may be used to diagnose acute infections
  • Lymphopenia and elevated transaminases are non-specific, but may indicate worse prognosis


  • Supportive care is the hallmark of management
  • Strict isolation precautions: standard, contact and droplet
    • Limit entry and maintain a log of people who enter the room
  • Ribavirin has been shown to decrease mortality
    • Most effective when given early (within 6 days)


  • Admit (consider ICU admission)
  • Those that seek medical care are more likely to have serious infections:
    • Hospital mortality rates can reach 25%
    • Overal mortality rates are much less; around 5000 deaths per 100,000-300,000 infections annually

External Links

See Also