Health Professionals

Clinical Updates

3 February 2012

Lassa fever in Nigeria

The Nigerian Federal Ministry of Health has confirmed an increase in Lassa fever cases since the beginning of January 2012. A total of 27 suspected cases, 16 laboratory confirmed cases and 9 deaths (CFR 33.3%) have been reported [1].

Lassa fever

Lassa fever, named after the town in north-eastern Nigeria where the disease was first described, is an acute viral haemorrhagic fever caused by Lassa virus, a member of the arenavirus family. Lassa fever is also endemic in Guinea, Liberia,and Sierra Leone. Evidence of infection has also been found in the Central African Republic, Mali and Senegal.

Lassa fever is most commonly transmitted to humans following contamination of broken skin or mucous membranes with urine or droppings of the multimammate rats (Mastomys spp.) living around homes in rural areas of endemic countries. Person to person transmission can occur after direct contact with the body fluids of individuals with Lassa fever, usually in hospitals or healthcare settings.

A total of 12 imported cases of Lassa fever have been reported in the UK since 1970, including five from Nigeria [2]. The two most recent cases occurred in 2009, in travellers who had returned from Nigeria and Mali [3,4].

Advice for travellers

The risk of Lassa fever for travellers is very low [5]. Travellers at greater risk include those living or working in endemic areas, particularly healthcare or humanitarian aid workers, or those undertaking rural pursuits (e.g. camping) or work activities, where contact with rodents may be more likely [6].


There is no vaccine available to protect against Lassa fever. Travellers to endemic countries should avoid contact with rodents. Rodent populations can be reduced by clearing rubbish around dwellings, and preventing rodent access into buildings.

Healthcare workers should use personal protection measures when caring for persons suspected to have Lassa fever. See the WHO guidelines which are for designed for use in endemic settings: Infection control for viral haemorrhagic fevers in the African health care setting.

Advice for Health Professionals

Health professionals who suspect Lassa fever in a returned traveller must contact the Health Protection Agency’s Duty Doctor for advice on 020 8200 4400 as a matter of urgency.

More information about Lassa and other viral haemorrhagic fevers (including the Guidelines for management and control) is available from the Health Protection Agency.


1. Federal Ministry of Health, Nigeria. Weekly Updates on Epidemics in Nigeria. January 2012. [Accessed 03 February 2012]. Available at:

2. Health Protection Agency. Table of imported confirmed cases of Lassa fever in UK since 1970. [Accessed 03 February 2012]. Available at:



3. NaTHNaC. Imported case of Lassa fever in the United Kingdom, 30 January 2009. [Accessed 03 February 2012]. Available at:


4. Health Protection Agency. Patient dies from Lassa fever at a London hospital, 17 February 2009. [Accessed 03 February 2012]. Available at:


5. Health Protection Agency. Lassa fever Africa. [Accessed 03 February 2012]. Available at:


6. Beeching NJ, Fletcher TE, Hill DR, Fletcher TE. Travellers and viral haemorrhagic fevers: what are the risks? Int J Antimicrob Ag. 36 (S1):S26-S35, 2010. [Accessed 03 February 2011]. Available at: 


Health Protection Agency. Lassa fever – Questions and Answers.

NaTHNaC: Outbreak Surveillance