Lassa fever

Lassa fever
Other names	Lassa hemorrhagic fever
Community education material for Lassa fever
Specialty	Infectious disease
Symptoms	Fever, headaches, bleeding[1]
Complications	Partial or complete, temporary or permanent hearing loss[1]
Usual onset	1–3 weeks following exposure[1]
Causes	Lassa virus[1]
Risk factors	Exposure to rodents in West Africa[1]
Diagnostic method	Laboratory testing[1]
Differential diagnosis	Ebola, malaria, typhoid fever[1]
Treatment	Supportive[1]
Prognosis	~1% risk of death with treatment[1]
Frequency	400,000 cases per year[2]
Deaths	5,000 deaths per year[2]

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]