Hepatitis A is one of five human hepatitis viruses (hepatitis A, B, C, D, and E) that primarily infect the liver and cause illness. An estimated 80,000 cases occur each year in the U.S., although much higher estimates have been proposed based on mathematical modeling of the past incidence of infection. Each year, an estimated 100 persons die as a result of acute liver failure in the U.S. due to hepatitis A, but the rate of infection has dramatically decreased since the hepatitis A vaccine was licensed and became available in the U.S. in 1995.
Hepatitis A is a communicable (or contagious) disease that spreads from person-to-person. It is spread almost exclusively through fecal-oral contact, generally from person-to-person, or via contaminated food or water. Food contaminated with the virus is the most common vehicle transmitting hepatitis A. The food preparer or cook is the individual most often contaminating the food, although he or she is generally not ill at the time of food preparation. The peak time of infectivity, when the most virus is present in the stool of an infectious individual, is during the two weeks before illness begins. Although only a small percentage of hepatitis A infections are associated with foodborne transmission, foodborne outbreaks have been increasingly implicated as a significant source of hepatitis A infection.
Hepatitis A may also be spread by household contact among families or roommates, sexual contact, ingestion of contaminated water, ingestion of raw or undercooked fruits and vegetables or shellfish (like oysters), and from persons sharing illicit drugs. Children often have asymptomatic or unrecognized infections and can pass the virus through ordinary play to family members and other children and adults.