High Quality Content by WIKIPEDIA articles! Lassa fever is an acute viral hemorrhagic fever first described in 1969 in the town of Lassa, in Borno State, Nigeria located in the Yedseram river valley at the south end of Lake Chad. Clinical cases of the disease had been known for over a decade earlier but not connected with this viral pathogen. The infection is endemic in West African countries, and causes 300-500,000 cases annually with approximately 5,000 deaths. Outbreaks of the disease have been observed in Nigeria, Liberia, Sierra Leone, Guinea, and the Central African Republic, but it is believed that human infections also exist in Democratic Republic of the Congo, Mali, and Senegal. Its primary animal host is the Natal Multimammate Mouse, an animal indigenous to most of Sub-Saharan Africa. Although the rodents are also a source of protein for peoples of these areas, the virus is probably transmitted by the contact with the feces and urine of animals accessing grain stores inresidences.