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. 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.