Lassa fever

Background

• RNA virus of arenaviridae family
• endemic to parts of West Africa
  • 100,000-300,000 infections every year
• Animal vector: Multimammate Rat (Mastomys natalensis)
• Lassa fever is a viral hemorrhagic fever

Transmission

• 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

• Normal causes of acute fever!
• Malaria
• Dengue
• Leptospirosis
• Typhoid fever
• Typhus
• Viral hemorrhagic fevers
  • Ebola virus disease
  • Marburg virus disease
  • Lassa fever
  • Crimean-Congo hemorrhagic fever
• Chikungunya
• Yellow fever
• Rift valley fever
• Q fever
• Amebiasis
• Zika virus

Diagnosis

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

Management

• Isolation precautions: standard, contact and droplet
  • Isolate in a single room with the door closed
  • Limit entry and maintain a log of people who enter the room
  • Use standard, contact, and droplet precautions
• Ribavirin has been shown to decrease mortality
  • Most effective when given early (within 6 days)
• Supportive care

Disposition

• 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
• Admit, isolation, possible ICU for serologic results and clinical observation/supportive care

See Also

• Viral hemorrhagic fever

References

• Lassa Fever http://www.cdc.gov/vhf/lassa/index.html
• McCormick JB, King IJ, Webb PA, Scribner CL, Craven RB, Johnson KM, Elliott LH, BelmontWilliams R. Lassa fever. Effective therapy with ribavirin. N Engl J Med. 1986;314:20–26.