Health Professionals

Clinical Updates

21 May 2012

Lassa fever in Nigeria - update 3

This updates the information posted on Lassa Fever in Nigeria on 5 April 2012.

The outbreak of Lassa fever in Nigeria, first reported to the World Health Organization (WHO) by the Federal Ministry of Health, Nigeria in January 2012, is continuing [1]. As of 11 May 2012, a total of 869 suspected cases of Lassa fever have been reported including 143 laboratory confirmed cases and 92 deaths [2]. As of 11 May 2012,  22 of the 36 states of Nigeria have reported cases (Abuja Capital Territory, Abia, Adamawa, Anambra, Bauchi, Benue, Borno, Ebonyi, Edo, Gombe, Kaduna, Kano, Kogi, Lagos, Nassarawa, Ondo, Oyo, Plateau, Rivers, Sokoto, Taraba and Yobe ) [2, 3].

The most recent cases have been reported in Nasarawa, Plateau and Sokoto, the most affected states remain Edo and Taraba [3].


View a map of areas affected by Lassa fever outbreak as of 11 May 2012 [3].


The Federal and State governments responded to the outbreak by enhancing the disease surveillance for early detection and reinforcing treatment of patients [1, 3].

The response to the escalating outbreak is challenged by limited availability of resources [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. 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 [4]. The two most recent cases occurred in 2009, in travellers who had returned from Nigeria and Mali [5, 6].

Advice for travellers:

Currently there are no restrictions on travel or trade with Nigeria and Lassa fever is a rare risk for travellers [1, 7, 8]. 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 [8].

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.  Guidelines which are designated for use in endemic settings are available from WHO: 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. Expert advice can also be obtained from the HPA Rare and Imported Pathogens Laboratory.

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 21 May 2012]. Available at:

2. Federal Ministry of Health, Nigeria. Weekly Updates on Epidemics in Nigeria: as at 11TH May 2012. 18 May 2012. [Accessed 21 May 2012]. Available at:

3. Federal Ministry of Health, Nigeria. Weekly Updates on Epidemics in Nigeria: as at 11th May 2012.  21 May 2012. [Accessed 21 May 2012]. Available at:


4. Health Protection Agency. Table of imported confirmed cases of Lassa fever in UK since 1970. [Accessed 21 May 2012]. Available at:



5. NaTHNaC. Imported case of Lassa fever in the United Kingdom, 30 January 2009. [Accessed 21 May 2012]. Available at:

6. Health Protection Agency. Patient dies from Lassa fever at a London hospital, 18 February 2009. [Accessed 21 May 2012]. Available at:


7. Health Protection Agency. Lassa Fever Africa. [Accessed 21 May 2012]. Available at:


8. 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