In the United States and other industrialized countries, hepatitis is most often caused by viral infection. More than six types of hepatitis virus have now been identified. The most common is hepatitis A virus (HAV), which is spread by fecal–oral contamination, often by food handlers, and in crowded, unsanitary conditions. It may also be acquired by eating contaminated food, especially seafood. Hepatitis B virus (HBV) is spread by blood and other body fluids. It may be transmitted sexually, by sharing needles used for injection, and by close interpersonal contact. Infected individuals may become carriers of the disease. Most patients recover, but the disease may be serious, even fatal, and may lead to liver cancer. Hepatitis C is spread through blood and blood products or by close contact with an infected person. Hepatitis D, the delta virus, is highly pathogenic but only infects those already infected with hepatitis B. Hepatitis E, like HAV, is spread by contaminated food and water. It has caused epidemics in Asia, Africa, and Mexico. Hepatitis G is believed to be spread through contact with blood of an infected person. Vaccines are available for hepatitis A and B.

The name hepatitis simply means "inflammation of the liver," but this disease also causes necrosis (death) of liver cells. Hepatitis also may be caused by other infections and by drugs and toxins. Liver function tests performed on blood serum are important in diagnosis.

Jaundice, or icterus, is a symptom of hepatitis and other diseases of the liver and biliary system. It appears as yellowness of the skin, whites of the eyes, and mucous membranes caused by the presence of bile pigments, mainly bilirubin, in the blood.

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