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Rotavirus is the most common cause of severe diarrhoea among infants and young children.〔 It is a genus of double-stranded RNA virus in the family ''Reoviridae''. Nearly every child in the world has been infected with rotavirus at least once by the age of five.〔 Immunity develops with each infection, so subsequent infections are less severe; adults are rarely affected.〔 There are eight species of this virus, referred to as A, B, C, D, E, F, G and H. ''Rotavirus A'', the most common species, causes more than 90% of rotavirus infections in humans. The virus is transmitted by the fæcal-oral route. It infects and damages the cells that line the small intestine and causes gastroenteritis (which is often called "stomach flu" despite having no relation to influenza). Although rotavirus was discovered in 1973 by Ruth Bishop and her colleagues by electron micrograph images〔 and accounts for up to 50% of hospitalisations for severe diarrhoea in infants and children,〔 its importance has been underestimated within the public health community, particularly in developing countries.〔 In addition to its impact on human health, rotavirus also infects animals, and is a pathogen of livestock.〔 Rotavirus is usually an easily managed disease of childhood, but worldwide more than 450,000 children under five years of age still die from rotavirus infection each year,〔 most of whom live in developing countries, and almost two million more become severely ill.〔 In the United States, before initiation of the rotavirus vaccination programme, rotavirus caused about 2.7 million cases of severe gastroenteritis in children, almost 60,000 hospitalizations, and around 37 deaths each year.〔 Public health campaigns to combat rotavirus focus on providing oral rehydration therapy for infected children and vaccination to prevent the disease.〔 The incidence and severity of rotavirus infections has declined significantly in countries that have added rotavirus vaccine to their routine childhood immunisation policies.〔〔 ==Signs and symptoms== Rotavirus gastroenteritis is a mild to severe disease characterised by nausea, vomiting, watery diarrhoea, and low-grade fever. Once a child is infected by the virus, there is an incubation period of about two days before symptoms appear. The period of illness is acute. Symptoms often start with vomiting followed by four to eight days of profuse diarrhoea. Dehydration is more common in rotavirus infection than in most of those caused by bacterial pathogens, and is the most common cause of death related to rotavirus infection. Symptoms of dehydration associated with Rotavirus include dizziness while standing, decrease in urination and dry mouth and throat. Rotavirus A infections can occur throughout life: the first usually produces symptoms, but subsequent infections are typically mild or asymptomatic, as the immune system provides some protection. Consequently, symptomatic infection rates are highest in children under two years of age and decrease progressively towards 45 years of age.〔Free ebook ()〕 Infection in newborn children, although common, is often associated with mild or asymptomatic disease;〔 the most severe symptoms tend to occur in children six months to two years of age, the elderly, and those with compromised or absent immune system functions. Due to immunity acquired in childhood, most adults are not susceptible to rotavirus; gastroenteritis in adults usually has a cause other than rotavirus, but asymptomatic infections in adults may maintain the transmission of infection in the community. 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「rotavirus」の詳細全文を読む スポンサード リンク
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