Lassa fever is a viral hemorrhagic fever caused by an arenavirus discovered in 1969 in Nigeria. The disease is endemic in Guinea, Sierra Leone, Liberia, Nigeria, southern Mali, and northern Cote d’Ivoire (Figure 1). In the last years, some cases appeared in Togo and the Republic of Benin. The disease would affect 900,000 persons per year, leading to 18,000 deaths in West Africa. The symptoms can range from mild flu-like to fulminant haemorrhagic fever, including, fever, headache, thoracic or lumbar pain, myalgia, nausea and vomiting, cough, pharyngia, diarrhea, oedema and bleeding.
The Natal multimammate mouse, Mastomys natalensis has been the main known reservoir of Lassa virus until recent identification of other reservoirs, like Hylomyscus pamfi,Mastomys erythroleucus and Mus baoulei. It is suggested that humans become infected by eating food or touching objects contaminated with infected rodent urine, by hunting, trapping, butchering or eating rodents, and possibly by inhaling virus-laden particles. The rodent-to-human transmission is estimated to occur in 80% of the cases whereas a human-to-human transmission is estimated to occur in 20% of the cases in both the community and health facilities.