Microbiology · Other viruses and prions
Arenaviruses (Lassa and the South American haemorrhagic fevers) !
- Virus
- Enveloped
- Contact
- Droplet
- For completeness
Rodent-borne viruses that cause haemorrhagic fevers: Lassa in West Africa and Junín, Machupo, Guanarito and Sabiá in South America.
Updated 2026-11-01
Also called: Lassa fever, Argentine haemorrhagic fever, Bolivian haemorrhagic fever, Venezuelan haemorrhagic fever
At a glance
- Shape
- Spherical or pleomorphic, with internal ribosome granules ("sand")
- Genome
- Single-stranded, ambisense RNA, two segments
- Envelope
- Enveloped
- Family
- Arenaviridae (genus Mammarenavirus)
- Size
- About 50 to 300 nm
Morphology
- Particles containing host ribosomes, which look like grains of sand under the microscope
- Two RNA segments (S and L) with an ambisense strategy
- Also includes lymphocytic choriomeningitis virus of the house mouse
Transmission
- Contact with or inhalation of rodent urine, droppings or nests; contaminated food
- Rodent bites or scratches
- Lassa and Machupo can spread from person to person through blood and body fluids, mostly in hospitals with poor infection control
Reservoir: Rodents, each virus with its own species: Mastomys for Lassa; field mice for Junín, Machupo and Guanarito
Isolation precautions
What the care team adds to standard precautions.
- Contact
- Gown and gloves; dedicated equipment. For C. difficile, soap-and-water hand washing.
- Droplet
- Surgical mask within about a metre; single room.
Virulence factors
- Infects macrophages and dendritic cells and suppresses the early immune response
- Endothelial damage with capillary leak, bleeding and shock
- Lassa can damage the inner ear: deafness in survivors
Diseases it causes
- Lassa fever Viral haemorrhagic fevers (Ebola and others) →
- South American haemorrhagic fevers (Argentine, Bolivian, Venezuelan, Brazilian) Viral haemorrhagic fevers (Ebola and others) →
Clinical picture
- Incubation of 2 to 21 days with gradual onset of fever, weakness and headache
- In severe cases: bleeding, hypotension, shock, seizures and coma
- Lassa: most infections are mild; deafness in up to a quarter of survivors
- More severe in pregnancy
Diagnosis
- RT-PCR, antigen or antibody ELISA
- Samples are a high biohazard: maximum-containment laboratories
- Early on it is confused with malaria and other fevers
Treatment
Intensive supportive care. Ribavirin has been used in Lassa fever, although its benefit is uncertain; convalescent plasma is used in Argentine haemorrhagic fever.
Drug class only; doses and regimens are set by the clinician from the current guideline.
In Pharmacology:
Prevention
- Store food in closed containers and control rodents in the home
- Barrier measures against blood and body fluids in hospital
- Junín virus vaccine in Argentina for people at risk
Test yourself
Think of the answer, then tap the question to see it.
What is the reservoir of Lassa virus?
The Mastomys rat (multimammate rat) of West Africa.
Which sequel is characteristic of Lassa fever in survivors?
Sensorineural deafness, often permanent.
Which arenavirus causes Venezuelan haemorrhagic fever?
Guanarito virus.
Which antiviral has been used in Lassa fever?
Ribavirin, although its efficacy is not well established.
Related
Related conditions
← Back to the group: Other viruses and prions
Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Lassa fever (WHO, 2024); About Viral Hemorrhagic Fevers | Viral Hemorrhagic Fevers (VHFs) | CDC (CDC, 2024).
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Representative model, for educational purposes only.