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Hepatitis A (formerly known as infectious hepatitis) is an acute infectious disease of the liver caused by the hepatitis A virus (HAV). Many cases have few or no symptoms, especially in the young.〔 The time between infection and symptoms, in those who develop them, is between two and six weeks. When symptoms occur, they typically last eight weeks and may include nausea, vomiting, diarrhea, jaundice, fever, and abdominal pain.〔 Around 10–15% of people experience a recurrence of symptoms during the six months after the initial infection.〔 Acute liver failure may rarely occur with this being more common in the elderly.〔 It is usually spread by eating or drinking food or water contaminated with infected feces. Shellfish which have not been sufficiently cooked are a relatively common source. It may also be spread through close contact with an infectious person.〔 While children often do not have symptoms when infected, they are still able to infect others.〔 After a single infection, a person is immune for the rest of his or her life. Diagnosis requires blood testing, as the symptoms are similar to those of a number of other diseases.〔 It is one of five known hepatitis viruses: A, B, C, D, and E. The hepatitis A vaccine is effective for prevention.〔 Some countries recommend it routinely for children and those at higher risk who have not previously been vaccinated.〔〔 It appears to be effective for life.〔 Other preventive measures include hand washing and properly cooking food.〔 No specific treatment is available, with rest and medications for nausea or diarrhea recommended on an as-needed basis.〔 Infections usually resolve completely and without ongoing liver disease.〔 Treatment of acute liver failure, if it occurs, is with liver transplantation.〔 Globally, around 1.5 million symptomatic cases occur each year〔 with likely tens of millions of infections in all. It is more common in regions of the world with poor sanitation and not enough safe water. In the developing world, about 90% of children have been infected by age 10, thus are immune by adulthood.〔 It often occurs in outbreaks in moderately developed countries where children are not exposed when young and vaccination is not widespread.〔 In 2010, acute hepatitis A resulted in 102,000 deaths. World Hepatitis Day occurs each year on July 28 to bring awareness to viral hepatitis.〔 ==Signs and symptoms== Early symptoms of hepatitis A infection can be mistaken for influenza, but some sufferers, especially children, exhibit no symptoms at all. Symptoms typically appear 2 to 6 weeks (the incubation period) after the initial infection. 90% of children do not have symptoms. The time between infection and symptoms, in those who develop them, is between two and six weeks with an average of 28 days.〔 The risk for symptomatic infection is directly related to age, with more than 80% of adults having symptoms compatible with acute viral hepatitis and the majority of children having either asymptomatic or unrecognized infections. Symptoms usually last less than 2 months, although some people can be ill for as long as 6 months: * Fatigue * Fever * Nausea * Appetite loss * Jaundice, a yellowing of the skin or whites of the eyes due to hyperbilirubinemia * Bile is removed from blood stream and excreted in urine, giving it a dark amber colour * Diarrhea * Light, or clay-coloured faeces (acholic faeces) 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「Hepatitis A」の詳細全文を読む スポンサード リンク
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