Lassa fever

This is a tropical infectious disease caused by the Lassa virus.


This is a tropical infectious disease caused by the Lassa virus. It presents with a constantly high fever, accompanied by headaches, a sore throat and muscle pain as well as a skin rash. In severe cases bleeding occurs, various organs can suffer damage, and the disease can be fatal. Obtaining medical advice for travellers before leaving on a trip is a good idea.


  • Incubation period: 6-21 days
Mild progression
Complications/severe progression

In particular in the case of a weakened immune system or pregnancy

Causes and treatment


  • Pathogen: Lassa virus
  • Transmission
    • Rodents: contact, excretions, contaminated food, infected dust
    • Human-to-human: droplet/wound infection, secretions, sexual intercourse

Further treatment by your doctor / in hospital

Possible tests
  • Physical examination
  • Examination of blood, urine or tissue samples in high-security laboratories
Possible therapies
  • Isolation (risk of contagion)
    • Persons you've been in contact with also have to be examined and isolated, if necessary
  • Treatment of symptoms
    • Medication (fever/painkillers)
    • Control coagulation
    • Replace lost fluids
  • Antiviral medication (ribavirin)
    • Only for severe cases
    • Viral suppression
    • This can have severe side-effects

What can I do myself?

  • Don’t travel if you're pregnant (severe disease course)
  • Medical advice for travellers before every trip to the tropics
  • Rodents
    • Avoid contact with mice and other rodents
    • Dispose of food suspected to have been contaminated by rodents
  • Regularly sanitise your hands

When to see a doctor?

  • Fever during or up to three weeks after returning from a trip to the tropics or subtropics
  • Bleeding into the skin
  • Feeling of being very unwell

Further information

Ostschweizer Infostelle für Reisemedizin (Eastern Switzerland Information Centre for Travel Medicine)

Swiss Tropical and Public Health Institute (Schweizerisches Tropen- und Public Health-Institut)

FDFA (travel links)


Lassa fever, Lassa fever and Lassa haemorrhagic fever, Lassa haemorrhagic fever

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CSS offers no guarantee for the accuracy and completeness of the information. The information published is no substitute for professional advice from a doctor or pharmacist.

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