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Biological Health Hazard – (Fatal) Lassa Hemorrhagic Fever (LHF) Outbreak: West Africa


Published Date: 2017-03-12 20:06:23
Subject: PRO/AH/EDR> Lassa fever – West Africa (10): Benin, Togo, Burkina Faso
Archive Number: 20170312.4896305

West Africa Map

Political West Africa Map. Map is showing the countries of the western part of Africa with international borders, the national capitals, and the largest cities. Image: Nations Online Project.

Date: Fri 10 Mar 2017
Source: WHO Emergency Preparedness Response [edited]

On 20 Feb 2017, the Ministry of Health of Benin notified WHO of a Lassa fever case in Tchaourou district, Borgou Department, Benin, close to the border with Nigeria. The case was a pregnant woman who was living in Nigeria (close to the border with Benin).

On 11 Feb 2017, she was admitted to a hospital where she delivered the baby (a premature neonate) by caesarean section and passed away on 12 Feb 2017. Samples were tested positive for Lassa fever in the laboratory in Cotonou, Benin and later in the Lagos University Teaching Hospital Lassa laboratory in Nigeria. The newborn and father left the hospital without notice on 14 Feb 2017 and went to Mango in northern Togo where they were admitted to a hospital.

The newborn tested positive for Lassa fever, and the father tested negative in the Institut National d’Hygiène in Lomé, Togo. The baby was treated with ribavirin and is currently in stable condition; he is still hospitalised in northern Togo for issues of prematurity and overall monitoring.

A total of 68 contacts are being followed-up in Benin, and 29 contacts are being followed-up in Togo linked to the pregnant woman and newborn.

Togo, exported from Burkina Faso

On 26 Feb 2017, after receiving information from Togo, the Ministry of Health of Burkina Faso has notified WHO of a confirmed Lassa fever case in a hospital in the northern part of Togo. The case originated from Ouargaye district, which is in the central eastern part of Burkina Faso.

The case was a pregnant woman who was previously hospitalized in Burkina Faso. She was discharged and had a miscarriage at home. After the 2nd hospitalization in Burkina Faso, she was transmitted to a hospital in Mango, northern Togo, and passed away on 3 Mar 2017.

Samples from the pregnant woman tested positive for Lassa fever at the Institut National d’Hygiène in Lomé, Togo.

A total of 7 contacts have been identified in Togo linked to the pregnant woman, and contact tracing is ongoing; 135 contacts in Burkina Faso have been identified linked to the pregnant woman, and contact tracing is ongoing.


On 2 Mar 2017, a man was admitted to a health centre in the Kpendial health district for fever and melena and was referred to a regional hospital on 3 Mar 2017.

Samples from the male case were sent to the Institut National d’Hygiène in Lomé, Togo and tested positive for Lassa fever. The case left the hospital on 6 Mar [2017]. Investigations are ongoing. The male case and his close relatives are under follow up at their home.

A total of 18 contacts were identified in Togo linked to the male case.

Public health response

Health authorities in Benin, Burkina Faso and Togo are implementing the following measures to respond to these Lassa fever cases, including:

– Deployment of rapid response teams to the affected areas for epidemiological investigation.
– Identification of contacts and follow-up.
– Strengthening of infection prevention and control measures in health facilities and briefing of health workers.
– Strengthening of cross border collaboration and information exchanges between Togo, Burkina, Mali and Benin.

WHO risk assessment

Lassa fever is an acute viral haemorrhagic fever illness. The Lassa virus is transmitted to humans via contact with food or household items contaminated with rodent urine or faeces. Person-to-person infections and laboratory transmission can also occur.

Lassa fever is endemic in neighbouring Nigeria and other West African countries and causes outbreaks almost every year in different parts of the region, with yearly peaks observed between December and February. The most recent Lassa fever outbreak in Benin occurred in the same area in January-May 2016. At least 54 cases including 28 deaths have been reported at country level. Both Burkina Faso and Togo have reported sporadic cases in the past.

Given constant important population movements between Nigeria, Togo, Burkina Faso, Niger and Benin, the occurrence of sporadic Lassa fever cases in West Africa was expected, and further sporadic cases may occur in countries of the region.

However, with the ongoing control measures in Benin, Togo and Burkina Faso, the risk of further disease spread from these confirmed cases is considered to be low. Considering the seasonal peaks in previous years, increase in disease awareness, better preparedness and response in general, and strengthening of regional collaboration, the risk of large scale outbreaks in the region is medium.

WHO advice

Prevention of Lassa fever relies on promoting good “community hygiene” to discourage rodents from entering homes. In health-care settings, staff should always apply standard infection prevention and control precautions when caring for patients, regardless of their presumed diagnosis.

On rare occasions, travelers from areas where Lassa fever is endemic export the disease to other countries. Although other tropical infections are much more common, the diagnosis of Lassa fever should be considered in febrile patients returning from West Africa, especially if they have had exposures in rural areas or hospitals in countries where Lassa fever is known to be endemic. Health-care workers seeing a patient suspected to have Lassa fever should immediately contact local and national experts for advice and to arrange for laboratory testing.

Communicated by:
ProMED-mail Rapporteur Marianne Hopp

[Lassa fever virus is endemic in much of northwest Africa, including Benin, Togo, and Burkina Faso. The previously reported reappearance of Lassa fever cases in Benin, with 61 cases reported in the north of the country, is of concern. The circumstances under which the above fatal Lassa fever patients acquired their virus infections are not stated but are apparently presumed to be due to exposure to rodents and their excreta. Because there can be person-to-person transmission via contact with viremic blood or secretions of infected patients, contact tracing is prudent. In hospitals treating Lassa fever patients, adequate patient isolation and use of personal protection equipment for treatment of infected patients are essential for safety.

The virus is a member of the family Arenaviridae and causes acute hemorrhagic fever. It is transmitted to humans from contact with food or household items contaminated with excreta of multimammate rats (_Mastomys_ spp), the reservoir host.

Public education is an important measure to prevent infections in the home. Virus transmission can occur in houses or in hospital environments or laboratories in the absence of adequate infection control measures.

Images of _Mastomys_ mice can be seen at

Maps of Benin and adjoining Togo and Burkina Faso can be accessed at and – Mod.TY

A HealthMap/ProMED-mail map can be accessed at:,]

See Also

Lassa fever – West Africa (08): Benin 20170301.4872702

Lassa fever – West Africa (09): Nigeria, Benin 20160227.4054108
Lassa fever – West Africa (07): Benin 20160221.4037846
Lassa fever – West Africa (04): Benin 20160209.4007158
Lassa fever – West Africa (02): Benin 20160206.3999178
Lassa fever – West Africa: Nigeria, Benin 20160131.3980796

Lassa fever – Benin (02): (AK) 20141126.2992727
Lassa fever – Benin: (AK) 20141124.2984679

A ProMED-mail post
ProMED-mail is a program of the International Society for Infectious Diseases

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