Posted on 29TH MAR 2017
tagged Lassa Fever, West Africa

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

Date: Mon 27 Mar 2017
Source: Outbreak News Today [edited]

Lassa fever outbreaks have been confirmed across 5 West African countries, including Nigeria, Benin, Sierra Leone, Togo, and Burkina Faso.

In Nigeria, the index case emerged on 16 Dec 2016 in Ogun state. Since then, the outbreak has remained active. During the week ending 19 Mar 2017, 15 suspected cases were reported, with 2 testing positive for Lassa fever. Between 16 Dec 2016 and 19 Mar 2017, a total of 283 suspected cases including 56 deaths (case fatality rate of 19.8 percent) have been reported. Of the suspected cases, 99 were confirmed by the Lagos University Teaching Hospital Lassa laboratory in Nigeria.

The cases have been distributed across 13 states: Ogun, Bauchi, Plateau, Ebonyi, Ondo, Edo, Taraba, Nasarawa, Rivers, Kaduna, Gombe, Cross-River, and Borno.

The outbreak of Lassa fever in Benin started on 12 Feb 2017 from Tchaourou district, Borgou province, close to the border with Nigeria. It was established that this case had epidemiological link with the ongoing Lassa fever outbreak in Nigeria. On 23 Feb 2017, another suspected case from L'Atacora province was reported. Samples obtained from the 2 cases tested positive for Lassa fever in the laboratory in Cotonou, Benin, and in the Lagos University Teaching Hospital Lassa laboratory. Both cases died, giving a case fatality of 100 percent.

In Togo, Lassa fever was confirmed on 23 Feb 2017, with the case having established epidemiological linkage to Benin. A total of 12 suspected were subsequently reported, 7 of them were confirmed at the Institut National d'Hygiene in Lome, Togo. 4 of the confirmed cases died, giving a case fatality rate of 57 percent. The cases originated from Oti and Kpendjal districts.

Burkina Faso
On 26 Feb 2017, the Ministry of Health of Burkina Faso notified WHO of a confirmed Lassa fever case admitted in a hospital in the northern part of Togo. The case originated from Ouargaye district, central eastern part of Burkina Faso. Burkina Faso has not had any other case.

Sierra Leone
Sierra Leone has been reporting sporadic suspected cases of Lassa fever since 28 Dec 2016. However, the outbreak situation escalated in the months of February and March 2017 when a cluster of 24 cases were reported and investigated. Out of these, 4 cases were laboratory confirmed and all of them died, thus giving case fatality rate of 100 percent among the confirmed. The outbreak has since subsided.

Lassa fever is endemic in Nigeria and other West African countries. Outbreaks have occurred almost every year in different parts of the region, with yearly peaks observed between December and February.

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ProMED-mail from HealthMap Alerts

[The West African countries mentioned in the report above can be located on the maps at and

Lassa virus is a member of the family Arenaviridae and can cause acute hemorrhagic fever in humans. Lassa fever is a zoonotic disease, meaning that humans become infected from contact with infected animals. The animal reservoir, or host, of Lassa virus is a rodent of the genus _Mastomys_, commonly known as the "multimammate rat." _Mastomys_ rats infected with Lassa virus do not become ill, but they can shed the virus in their urine and faeces (

Because the clinical course of the disease is so variable, detection of the disease in affected patients has been difficult. When presence of the disease is confirmed in a community, however, prompt isolation of affected patients, good infection prevention and control practices, and rigorous contact tracing can stop outbreaks. About 80 percent of people who become infected with Lassa virus have no symptoms. 1 in 5 infections result in severe disease, where the virus affects several organs such as the liver, spleen, and kidneys.

Considering the seasonal flare ups of cases during this time of the year, countries in West Africa that are endemic for Lassa fever are encouraged to strengthen their related surveillance systems.

Health-care workers caring for patients with suspected or confirmed Lassa fever should apply extra infection control measures to prevent contact with the patient's blood and body fluids and contaminated surfaces or materials such as clothing and bedding. When in close contact (within 1 metre/39 in.) of patients with Lassa fever, health-care workers should wear face protection (a face shield or a medical mask and goggles), a clean, non-sterile long-sleeved gown, and gloves (sterile gloves for some procedures).

Laboratory workers are also at risk. Samples taken from humans and animals for investigation of Lassa virus infection should be handled by trained staff and processed in suitably equipped laboratories under maximum biological containment conditions.

The diagnosis of Lassa fever should be considered in febrile patients returning from areas where Lassa fever is 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 ( - Mod.UBA]

See Also

Lassa fever - West Africa (12): Nigeria 20170327.4929174
Lassa fever - West Africa (11): Nigeria 20170319.4911462
Lassa fever - West Africa (10): Benin, Togo, Burkina Faso 20170312.4896305
Lassa fever - West Africa (09): Nigeria (BO) 20170302.4875164
Lassa fever - West Africa (08): Benin 20170301.4872702
Lassa fever - West Africa (07): Nigeria (BA) 20170225.4864837
Lassa fever - West Africa (06): Nigeria 20170225.4862689
Lassa fever - West Africa (05): Nigeria (NA) 20170215.4842179
Lassa fever - West Africa (04): Liberia 20170209.4827934
Lassa fever - West Africa (03): Nigeria (RI) 20170122.4782917
Lassa fever - West Africa (02): Nigeria (NA) 20170118.4773375
Lassa fever - West Africa (01): Nigeria (OG) 20170101.4735363