Hepatitis A infection is caused by hepatitis A virus (HAV). Hepatitis occurs when the body's immune response against the infected liver cells damages them, causing liver inflammation. It is usually transmitted from person to person through stool or feces. For example, this can happen when someone with the hepatitis A virus handles food without washing his or her hands after using the toilet, and the food is then ingested by a consumer. Hepatitis A can also be contracted by drinking contaminated water, eating raw shellfish from water polluted with sewage, or from being in close contact with a person who is infected, even if that person has no signs or symptoms. In fact, the disease is most contagious before signs and symptoms ever appear. The hepatitis A virus is shed in the stools (feces) 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.
Once the hepatitis A infection has resolved (usually within 3 to 6 months), the virus does not remain in the body, so those infected are no longer contagious to others nor do those who have had hepatitis A ever get it again.