Hepatitis A, caused by infection with the Hepatitis A virus (HAV), has an incubation period of approximately 28 days (range: 15 to 50 days). HAV replicates in the liver and is shed in high concentrations in feces from 2 weeks before to 1 week after the onset of clinical illness. HAV infection produces a self-limited disease that does not result in chronic infection or chronic liver disease.
However, 10 to 15% of patients might experience a relapse of symptoms during the 6 months after the acute illness. Acute liver failure from Hepatitis A is rare (overall case-fatality rate: 0.5%). The risk for symptomatic infection is directly related to age, with more than 80% of adults having symptoms compatible with acute viral hepatitis while the majority of children are either asymptomatic or have unrecognized infection. Antibody produced in response to HAV infection persists for life, and confers protection against reinfection.
HAV infection is primarily transmitted by the fecal-oral route, either by person-to-person contact or through consumption of contaminated food or water. Although viremia occurs early in infection and can persist for several weeks after onset of symptoms, bloodborne transmission of HAV is uncommon.
In the United States, nearly half of all reported Hepatitis A cases have no specific risk factor identified. Among adults with identified risk factors, the majority of cases are among men who have sex men (MSM), persons who use illegal drugs, and international travelers.
Because transmission of HAV during sexual activity probably occurs because of fecal-oral contact, measures typically used to prevent the transmission of other sexually transmitted diseases (STDs), such as use of condoms, do not prevent HAV transmission. In addition, efforts to promote good personal hygiene generally have not been successful in interrupting outbreaks of Hepatitis A. Vaccination is the most effective means of preventing HAV transmission among persons at risk for infection. Hepatitis A vaccination is recommended for all children at 1 year of age, for persons who are at increased risk for infection (e.g., men who have sex with men), for persons who are at increased risk for complications from Hepatitis A, and for any person wishing to obtain immunity.