Lassa virus LASV (strain Josiah), isolated in Sierra Leone, is a virus member of the family Arenaviridae. In humans can cause hemorrhagic fever.
Lassa virus LASV (strain Nigeria), isolated in Nigeria, is a virus member of the family Arenaviridae. In humans can cause hemorrhagic fever.
It is endemic in West African countries, especially Sierra Leone, the Republic of Guinea, Nigeria, and Liberia, where the annual incidence of infection is between 300,000 and 500,000 cases, resulting in 5,000 deaths per year. The geographically restricted occurrence of the disease is not well understood as its rodent host (Mastomys species) is prevalent in much larger areas of sub-Saharan Africa.
Many of those infected by the virus do not develop symptoms. When symptoms occur they typically include fever, weakness, headaches, vomiting, and muscle pains. Less commonly there may be bleeding from the mouth or gastrointestinal tract. Other conditions that may present similarly include Ebola, malaria, typhoid fever, and yellow fever.
The disease is usually initially spread to people via contact with the urine or feces of an infected multimammate mouse or via direct contact between people.