16 March 2009
Lassa fever in Nigeria
As of 2 March 2009, seven cases of Lassa fever, including two deaths, were confirmed in the states of Edo and Ondo . Unverified media reports have also reported an increase in Lassa fever activity in Abuja Federal Capital Territory and Nassawara state, with over 93 cases reported between December 2008 and 5 March 2009 .
Lassa fever is an acute viral haemorrhagic fever caused by Lassa virus, a member of the arenavirus family. It is endemic in Guinea, Liberia, Nigeria and Sierra Leone. Evidence of infection has also been found in the neighbouring countries of Central African Republic, Mali and Senegal.
Lassa fever is most commonly transmitted to humans following contamination of broken skin or mucous membranes with the urine or droppings of rats that live around homes in rural areas of endemic countries. Person to person transmission can occur after direct contact with the bodily fluids of persons who have Lassa fever, usually in the healthcare setting.
Advice for travellers
The risk of Lassa fever in travellers is extremely low. In January and February 2009, two imported cases were reported in the UK. The first was in a traveller who had returned from Nigeria [3,4], and the second in a traveller who had returned from Mali [5, 6]. Prior to these cases there had been six cases of Lassa fever imported into the UK since 1976, all of which occurred in high risk travellers such as those working in the medical or aid sectors .
There is no vaccine available to protect against Lassa fever. Travellers to endemic countries should avoid contact with rodents; rodents excrete virus in their urine and faeces. 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: Infection control for viral haemorrhagic fevers in the African health care setting.
More information about Lassa and other viral haemorrhagic fevers (including the guidelines for management and control) is available from the Health Protection Agency website. Health professionals who suspect a case of Lassa fever in a returned traveller should contact the Health Protection Agency’s Duty Doctor on 020 8200 4400 for further advice.
1. World Health Organization (Via ReliefWeb). Weekly Emergency Situation Update, 2 March 2009. [Accessed 13 March 2009]. Available at: http://www.reliefweb.int/rw/RWFiles2009.nsf/FilesByRWDocUnid
2. United Nations Office for the Coordination of Humanitarian Affairs: Integrated Regional Information Networks (IRIN). Nigeria: Fighting lethal Lassa fever, 5 March 2009. [Accessed 13 March 2009]. Available at: http://www.irinnews.org/Report.aspx?ReportId=83309
3. NaTHNaC. Imported case of Lassa fever in the United Kingdom, 30 January 2009. [Accessed 13 March 2009]. Available at: https://www.nathnac.org/pro/clinical_updates/Lassa_300109htm
4. Health Protection Agency. Case of Lassa fever in a specialist unit in London, 23 January 2009. [Accessed 13 March 2009]. Available at: http://www.hpa.org.uk/webw/HPAweb&HPAwebStandard/HPAwe
5. Health Protection Agency. Patient dies from Lassa fever at a London hospital, 17 February 2009. [Accessed 13 March 2009]. Available at: http://www.hpa.org.uk/webw/HPAweb&HPAwebStandard/HPAw
6. EuroSurveillance. The first case of Lassa fever imported from Mali into the United Kingdom, February 2009, 12 March 2009. [Accessed 16 March 2009]. Available at: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=19145
7. Health Protection Agency. Lassa fever – questions and answers. [Accessed 13 March 2009]. Available at http://www.hpa.org.uk/webw/HPAweb&HPAwebStandard/HPAwe