The Travel Health and Vaccine Specialists

Lassa fever in West Africa

Level 1

Practise usual precautions

Updated: March 13, 2019


  • Information regarding Lassa fever in Nigeria was updated.
  • Sierra Leone has been added to the list of countries reporting cases of Lassa fever in 2019.

Original publication date: August 21, 2017

Current situation

Lassa fever is a known risk in West Africa.

Nigeria is currently experiencing a large outbreak of Lassa fever. Since the outbreak was declared on January 22nd, 2019, there has been over 420 confirmed cases and over 90 deaths reported. Suspected and/or confirmed cases have been reported in 21 of 36 states. Edo and Ondo states have reported the highest number of cases.

Since the beginning of 2019, the World Health Organization has also confirmed cases and/or outbreaks of Lassa fever in:

  • Benin
  • Guinea
  • Liberia
  • Nigeria
  • Sierra Leone
  • Togo

About Lassa fever

Lassa fever is caused by the Lassa virus. Lassa virus is most commonly spread through the urine and feces of infected rats.

This includes:

  • direct contact with rat urine or feces
  • touching objects soiled with urine or feces
  • exposure of open cuts or sores
  • eating contaminated food
  • breathing in dust or dirt that is contaminated with the virus (which can happen during cleaning activities like sweeping or dusting)

Those who are most at risk of getting Lassa fever:

  • live or work in areas with a risk of Lassa fever and have been exposed to infected rats or their urine and/or feces
  • provide care for patients in a community where the illness is present
  • are sexual partners of a male who is within 3 months of being infected

Lassa virus can also be spread between humans through direct contact with the blood, tissue, urine, feces or other bodily fluids of a person infected with Lassa fever.

Typically, about 1% of infected people will die from Lassa fever.

There is no vaccine or medication that protects against Lassa fever.


Most people infected with Lassa virus will have mild, or no symptoms. If symptoms occur, they are usually gradual and include:

  • fever
  • general weakness
  • headache
  • sore throat
  • chest and muscle pain
  • nausea and vomiting
  • diarrhea

In some instances, the illness can progress to a severe form with symptoms of:

  • face and neck swelling
  • respiratory distress
  • bleeding from the mouth, nose, vagina or gastrointestinal tract
  • shock
  • seizure
  • altered mental state

The disease is especially severe during late pregnancy when maternal death frequently occurs; fetal loss occurs in more than 80% of cases, particularly during the third trimester.

Recommendations for travellers

Consult a health care professional or visit a travel health clinic at least six weeks before you travel.

  • Avoid contact with rodents (rats), especially rat urine and feces.
    • Store food in rodent-proof containers
    • Dispose of garbage far from your living quarters
    • Maintain clean living quarters
    • Do not eat rats
    • Ensure that food is well cooked
    • If it is necessary to clean areas contaminated by rat urine or feces, follow proper safety precautions
  • Protect yourself from the spread of germs:
    • Wash your hands frequently with soap and water.
    • Keep your hands away from your face.
    • Do not share eating or drinking utensils.
    • Clean surfaces that are frequently touched (for example: doorknobs and counters).
    • Avoid close contact with sick people and their body fluids.
    • Practice safe sex and use condoms correctly.
    • Health care workers should follow strict infection control measures. This includes wearing all necessary personal protective equipment such as masks, gloves, gowns, and face shields when caring for patients with suspected or confirmed Lassa fever.
  • Monitor your health
    • If you develop symptoms of Lassa fever when you are travelling or after you return, see a health care professional. Tell them where you have been travelling or living.

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Report a problem or mistake on this pageShare this pageDate modified: 2017-04-05