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
- Chikungunya
- Yellow fever
- Rift valley fever
- Q fever
- Amebiasis
- Zika virus
Diagnostic Evaluation
- 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
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
External Links
- Lassa Fever http://www.cdc.gov/vhf/lassa/index.html