Outbreaks

· Previous outbreaks have been reported in Central African Republic, Liberia, Nigeria and Sierra Leone. Serological evidence of human infection has been found in Democratic Republic of the Congo, Guinea, Mali and Senegal.

· The most recent outbreak occurred in Sierra Leone. A total of 823 cases, including 153 deaths (18.6%), were reported from January 1996 to April 1997.

International implications As Lassa fever may have a long (up to 21 day) incubation period, it is possible that travellers from endemic areas may be incubating the disease. It is important that fevers of unknown origin in people coming from these endemic areas be investigated for the possibility of Lassa fever. However, one case of Lassa fever entering a non-endemic area should not arouse fear of an epidemic as long as it is ensured that the correct infection control procedures are followed.

For further information journalists can contact the Office of the Press Spokesperson, WHO, Geneva. Telephone (+41 22) 791 2599. Fax (+41 22) 791 4858. E-mail: inf@who.int All WHO Press Releases and Fact Sheets can be obtained on the Internet on the WHO home page https://www.who.int

© WHO/OMS, 1998