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Chikungunya ( ; Makonde for "that which bends up") is an infection caused by the chikungunya virus. The disease features the sudden onset of fever two to four days after exposure. The fever usually lasts two to seven days, while accompanying joint pains typically last weeks or months but sometimes years.〔 〕〔 The mortality rate is a little less than 1 in 1000, with the elderly or those with underlying chronic medical problems most likely having severe complications. The virus is passed to humans by two species of mosquito of the genus ''Aedes'': ''A. albopictus'' and ''A. aegypti''. Animal reservoirs of the virus include monkeys, birds, cattle, and rodents. This is in contrast to dengue, for which primates are the only hosts.〔(【引用サイトリンク】url=http://www.who.int/vaccine_research/diseases/vector/en/index1.html )〕 Since 2004, the disease has occurred in outbreaks in Asia, Europe and the Americas. The best means of prevention is overall mosquito control and the avoidance of bites by mosquitoes in areas where the disease is common.〔 This may be partly achieved with the use of mosquito nets. No specific treatment is known, but supportive care is recommended, including rest, fluids, and medications to reduce fever and joint pain. ==Signs and symptoms== The incubation period of the chikungunya virus ranges from one to twelve days, and is most typically three to seven. The disease may be asymptomatic, but generally is not, as 72% to 97% of those infected will develop symptoms.〔 Characteristic symptoms include sudden onset with high fever, joint pain, and rash. Other symptoms may occur, including headache, fatigue, digestive complaints, and conjunctivitis.〔 Information gained during recent epidemics suggests that chikungunya fever may result in a chronic phase as well as the phase of acute illness.〔 Within the acute phase, two stages have been identified: a viral stage during the first five to seven days, during which viremia occurs,〔 followed by a convalescent stage lasting approximately ten days, during which symptoms improve and the virus cannot be detected in the blood.〔 Typically, the disease begins with a sudden high fever that lasts from a few days to a week, and sometimes up to ten days. The fever is usually above 39 °C (102 °F) and sometimes reaching 40 °C (104 °F) and may be biphasic—lasting several days, breaking, and then returning. Fever occurs with the onset of viremia, and the level of virus in the blood correlates with the intensity of symptoms in the acute phase.〔 When IgM, an antibody that is a response to the initial exposure to an antigen, appears in the blood, viremia begins to diminish. However, headache, insomnia and an extreme degree of exhaustion remain, usually about five to seven days. Following the fever, strong joint pain or stiffness occurs; it usually lasts weeks or months, but may last for years. The joint pain can be debilitating, often resulting in near immobility of the affected joints. Joint pain is reported in 87–98% of cases, and nearly always occurs in more than one joint, though joint swelling is uncommon.〔 Typically the affected joints are located in both arms and legs, and are affected symmetrically. Joints are more likely to be affected if they have been previously been damaged by disorders such as arthritis.〔 Pain most commonly occurs in peripheral joints, such as the wrists, ankles, and joints of the hands and feet as well as some of the larger joints, typically the shoulders, elbows and knees.〔〔 Pain may also occur in the muscles or ligaments. Rash occurs in 40-50% of cases, generally as a maculopapular rash occurring two to five days after onset of symptoms.〔 Digestive symptoms, including abdominal pain, nausea, vomiting or diarrhea, may also occur.〔〔 In more than half of cases, normal activity is limited by significant fatigue and pain.〔 Infrequently, inflammation of the eyes may occur in the form of iridocyclitis, or uveitis, and retinal lesions may occur. Rarely, neurological disorders have been reported in association with chickungunya virus, including Guillain-Barré syndrome, palsies, meningoencephalitis, flaccid paralysis and neuropathy.〔 In contrast to dengue fever, Chikungunya fever very rarely causes hemorrhagic complications. Symptoms of bleeding should lead to consideration of alternative diagnoses or co-infection with dengue fever or coexisting congestive hepatopathy. 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「Chikungunya」の詳細全文を読む スポンサード リンク
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