Lassa fever | |
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Other names | Lassa hemorrhagic fever |
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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]
Lassa fever is endemic in West Africa.