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Hepatitis
Hepatitis (肝炎) is a disease characterized by inflammation (炎症) of and injury to the liver. The disease has many causes, including misuse of alcohol and drugs, but viruses are the most common cause. Researchers estimate that more than 300,000 cases of viral hepatitis Occur each year in the United States.
Symptoms of viral hepatitis appear from two weeks to six months after exposure to the virus. The first symptoms are usually fatigue, poor appetite and nausea. Pain in the abdomen above the liver and a slight fever are also common. After a few days, the person"s urine becomes dark and jaundice (黄疸) appears. The jaundice and dark urine indicate the liver is not working properly.
Symptoms of viral hepatitis generally last two to six weeks. Severe cases can lead to liver failure and death. But most patients—even those with severe hepatitis—eventually recover completely. In some patients, the disease becomes persistent and is called chronic hepatitis. Persons with chronic hepatitis may experience mild, vague symptoms of fatigue and poor appetite.
There are five types of viral hepatitis. Hepatitis A is a highly contagious disease, but it is rarely fatal. It is also called infectious hepatitis. Hepatitis A is extremely common in developing nations. Outbreaks often occur due to unsanitary conditions, such as contamination of food or the water supply.
Hepatitis B is the best-known form of viral hepatitis. It can be severe and often develops into chronic hepatitis. Hepatitis B is spread by close personal or sexual contact with an infected person or by exposure to infected blood.
Hepatitis C is usually spread by exposure to infected blood. It is the most common cause of transfusion-related hepatitis. It is also a common cause of chronic hepatitis. Hepatitis D is the most serious and also the rarest form of viral hepatitis. It only infects people who also have hepatitis B. Many cases of hepatitis D are fatal and most commonly occur among intravenous drug users, who can be infected by sharing hypodermic needles. Hepatitis E often occurs in epidemics that can be linked to poor hygiene and contaminated water. It is particularly likely to lead to serious illness in pregnant women. The disease has been reported almost exclusively in developing countries.