5 April 2012

Lassa fever in Nigeria - update 2

This updates the Clinical Update Lassa Fever in Nigeria  29 February 2012.

In January 2012, the Federal Ministry of Health in Nigeria notified the World Health Organization (WHO) of a Lassa fever outbreak [1]. The outbreak is continuing and as of 30 March 2012, 714 suspected cases (of which 110 have been laboratory confirmed) and 75 deaths have been reported [2]. The deaths include seven health workers: three doctors and four nurses [3]. The outbreak has so far affected 19 of the 36 states of Nigeria (Abuja Capital Territory, Abia, Adamawa, Anambra, Bauchi, Borno, Ebonyi, Edo, Gombe, Kaduna, Kano, Lagos, Nassarawa, Ondo, Oyo, Plateau, Rivers, Taraba and Yobe ) [1, 3].

The WHO produced a map showing the timeline of events relating to the outbreak [3].

Nigerian government authorities responding to the outbreak by enhancing disease surveillance , reinforcing treatment of patients, and conducting awareness campaigns among the affected population [1]. In addition, the International Federation of Red Cross and Red Crescent Societies are supporting the Nigerian Red Cross Society in delivering assistance to 15,000 households. Volunteers will carry out community activities to highlight good hygiene and the importance of case detection to help control disease spread [4].

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. In recent years, there is evidence of infection in the Central African Republic, Mali and Senegal.

Lassa fever is usually transmitted to humans after broken skin or mucous membranes are contaminated with urine or droppings from rats living near rural homes in endemic countries. Person to person transmission can occur after direct contact with body fluids of infected individuals, usually in hospital or healthcare settings.

A total of 12 imported cases of Lassa fever have been reported in the UK since 1970, including five from Nigeria [5]. The two most recent cases occurred in 2009, in travellers who had returned from Nigeria and Mali [6, 7].

Advice for travellers:

Currently there are no restrictions on travel or trade with Nigeria. Lassa fever is a rare risk for most travellers [1, 8, 9]. 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 [9].

There is no vaccine 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 WHO guidelines which are designated 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 UK Guidance for Management and Control) is available from the Health Protection Agency.


1. The World Health Organization. Global Alert and Response (GAR). Lassa fever in Nigeria. 4 April 2012. [Accessed 5 April 2012]. Available at:

2. Federal Ministry of Health, Nigeria. Weekly Updates on Epidemics in Nigeria: as at 30th March, 2012. 4 April 2012. [Accessed 5 April 2012]. Available at:

3. The World Health Organization. Nigeria: Lassa Fever outbreak (Situation as of 22 March 2012). 3 April 2012. [Accessed 5 April 2012]. Available at:

4. International Federation of Red Cross and Red Crescent Societies. Disaster Relief Emergency Fund (DREF). Nigeria: Lassa fever. 4 February 2012. [Accessed 5 April 2012]. Available at:

5. Health Protection Agency. Table of imported confirmed cases of Lassa fever in UK since 1970. [Accessed 5 April 2012]. Available at:



6. NaTHNaC. Imported case of Lassa fever in the United Kingdom, 30 January 2009. [Accessed 5 April 2012]. Available at:


7. Health Protection Agency. Patient dies from Lassa fever at a London hospital, 17 February 2009. [Accessed 5 April 2012]. Available at:


8. Health Protection Agency. Lassa Fever: Africa. [Accessed 5 April 2012]. Available at:


9. 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.


Health Protection Agency: Lassa Fever: Nigeria

Health Protection Agency: Lassa fever – Questions and Answers.

NaTHNaC: Outbreak Surveillance