Viral Hepatitis A

Epidemics of infectious jaundice have been reported throughout recorded history. However, the proof that many of these outbreaks and individual cases of acute hepatitis were caused by a viral infection, the hepatitis A virus (HAV), did not appear until the 1960s. After the transmission of infection to marmosets and humans, the epidemiologic and virologic characteristics that differed between hepatitis A and hepatitis B virus infections were defined more clearly. After the development and licensure of hepatitis A vaccines in the 1990s, it became possible to implement an effective prevention program involving routine immunization of young children in the United States and several other Western countries. However, despite the dramatic efficacy of the childhood immunization program in reducing the incidence of acute hepatitis from HAV in the population, older children and adults remained susceptible. Significant morbidity continues to occur in the United States among international travelers, injection drug users, persons with underlying liver disease, and other high-risk populations. Since HAV is a global pathogen, the prevention of increasing morbidity from hepatitis A attributable to