Lassa fever

Lassa fever, also known as Lassa hemorrhagic fever, is a type of viral hemorrhagic fever caused by the Lassa virus.^[1] Many of those infected by the virus do not develop symptoms.^[1] When symptoms occur, they typically include fever, weakness, headaches, vomiting, and muscle pains.^[1] Less commonly there may be bleeding from the mouth or gastrointestinal tract.^[1] The risk of death once infected is about one percent and frequently occurs within two weeks of the onset of symptoms.^[1] Of those who survive, about a quarter have hearing loss, which improves within three months in about half of these cases.^[1][3][4]

The disease is usually initially spread to people via contact with the urine or feces of an infected multimammate mouse.^[1] Spread can then occur via direct contact between people.^[1][5] Diagnosis based on symptoms is difficult.^[1] Confirmation is by laboratory testing to detect the virus's RNA, antibodies for the virus, or the virus itself in cell culture.^[1] Other conditions that may present similarly include Ebola, malaria, typhoid fever, and yellow fever.^[1] The Lassa virus is a member of the Arenaviridae family of viruses.^[1]

There is no vaccine.^[6] Prevention requires isolating those who are infected and decreasing contact with the mice.^[1] Other efforts to control the spread of disease include having a cat to hunt vermin, and storing food in sealed containers.^[1] Treatment is directed at addressing dehydration and improving symptoms.^[1] The antiviral medication ribavirin has been recommended,^[1] but evidence to support its use is weak.^[7][8]

Descriptions of the disease date from the 1950s.^[1] The virus was first described in 1969 from a case in the town of Lassa, in Borno State, Nigeria.^[1][9] Lassa fever is relatively common in West Africa including the countries of Nigeria, Liberia, Sierra Leone, Guinea, and Ghana.^[1][2] There are about 300,000 to 500,000 cases which result in 5,000 deaths a year.^[2][10]