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
    • No vaccination available
  • 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

Exclusion of liability

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.