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Lassa fever or Lassa hemorrhagic fever (LHF) is an acute viral hemorrhagic fever caused by the Lassa virus and first described in 1969 in the town of Lassa, in Borno State, Nigeria. Lassa fever is a member of the ''Arenaviridae'' virus family. Similar to ebola,〔Donaldson, Ross. The Lassa Ward. New York:St.Martin's Press, 2009〕 clinical cases of the disease had been known for over a decade, but had not been connected with a viral pathogen. Lassa frequently infects people in West Africa. It results in 300,000 to 500,000 cases annually and causes about 5,000 deaths each year. Outbreaks of the disease have been observed in Nigeria, Liberia, Sierra Leone, Guinea, and the Central African Republic. The primary animal host of the Lassa virus is the Natal multimammate mouse (''Mastomys natalensis''), an animal found in most of sub-Saharan Africa. The virus is probably transmitted by contact with the feces or urine of animals accessing grain stores in residences.〔 Given its high rate of incidence, Lassa fever is a major problem in affected countries. ==Signs and symptoms== In 80% of cases, the disease is asymptomatic, but in the remaining 20%, it takes a complicated course. The virus is estimated to be responsible for about 5,000 deaths annually. The fever accounts for up to one-third of deaths in hospitals within the affected regions and 10 to 16% of total cases.〔Centers for Disease Control and Prevention, ("Lassa Fever" )〕 After an incubation period of six to 21 days, an acute illness with multiorgan involvement develops. Nonspecific symptoms include fever, facial swelling, and muscle fatigue, as well as conjunctivitis and mucosal bleeding. The other symptoms arising from the affected organs are: * Gastrointestinal tract * * Nausea * * Vomiting (bloody) * * Diarrhea (bloody) * * Stomach ache * * Constipation * * Dysphagia (difficulty swallowing) * * Hepatitis * Cardiovascular system * * Pericarditis * * Hypertension * * Hypotension * * Tachycardia (abnormally high heart rate) * Respiratory tract * * Cough * * Chest pain * * Dyspnoea * * Pharyngitis * * Pleuritis * Nervous system * * Encephalitis * * Meningitis * * Unilateral or bilateral hearing deficit * * Seizures Clinically, Lassa fever infections are difficult to distinguish from other viral hemorrhagic fevers such as Ebola and Marburg, and from more common febrile illnesses such as malaria. The virus is excreted in urine for 3-9 weeks and in semen for three months. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Lassa fever」の詳細全文を読む スポンサード リンク
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