Definition of Hepatitis A:

Hepatitis A is an inflammation (irritation and swelling) of the liver caused by the hepatitis A virus.

Causes, incidence, and risk factors:

Hepatitis A is transmitted by contaminated food or water, or contact with a person who is currently ill with the disease. The hepatitis A virus is shed in the stools of an infected person during the incubation period of 15 to 45 days before symptoms occur and during the first week of illness. Blood and other bodily secretions may also be infectious.

The virus does not remain in the body after the infection has resolved, and there is no carrier state (a person or animal that spreads the disease to others but does not become ill).

The symptoms associated with hepatitis A are similar to the flu, but the skin and eyes may become yellow (jaundiced). This is because the liver is not able to filter bilirubin from the blood. There are approximately 100,000 total infections in the U.S. every year.

Risk factors include living in a nursing home or rehabilitation center, having a family member who recently had hepatitis A, intravenous drug use, and recent travel to -- or immigration from -- Asia, or South or Central America.

Other common hepatitis virus infections include hepatitis B and hepatitis C, but hepatitis A is the least serious and most mild of these diseases. Both of the others may become chronic illnesses, but hepatitis A does not.