Lassa fever

Lassa fever is a rare but serious infectious disease found in certain regions of West Africa. It is caused by a virus. Fortunately, most people do not become ill from the Lassa virus. In severe cases, however, the disease can lead to bleeding within the body. The virus is transmitted through direct contact with the bodily fluids of infected or deceased individuals, or rodents, such as blood, faeces, urine, vomit, semen, and sweat. The risk of travellers contracting Lassa fever is very low.

Where does Lassa fever occur?

Lassa fever is a rare disease that is primarily found in parts of West Africa, particularly in countries like Nigeria, Sierra Leone, Guinea, and Liberia.

What are the symptoms?

The majority of people (around 80%) do not fall ill after being infected with the Lassa virus. If symptoms do appear, they typically develop about nine days after infection. These symptoms may include:

• Fever
• Headache
• Muscle pain
• Sore throat
• Cough
• Abdominal pain
• Vomiting and/or diarrhoea
• Ulcers in the mouth (rare)
• Bleeding (rare)
• Coma (rare)

How to prevent Lassa fever?

The risk of travellers contracting Lassa fever in West Africa is very low. However, it is essential to follow general hygiene measures and avoid contact with sick or deceased patients, as well as their bodily fluids. It is also recommended to avoid mice, other wild animals, and the consumption of ‘bush meat’.

More information

Would you like to know more about Lassa fever? Please visit the RIVM information page: Lassa fever | RIVM.