Approximately 26 000 cases of acute HAV infection were reported annually in the United States prior to the advent of the HAV vaccine.1 The actual rate of infection was likely 10 times higher because most infections occur in young children, in whom the disease generally causes few or no symptoms.2 The virus is spread through fecal-oral transmission, and there is no evidence of a chronic carrier state or long-term sequelae. Historically, adult infections in the United States originated from contact with a child who had unrecognized infection or through epidemics attributable to contaminated food or water.3 In developing countries, where childhood infection is prevalent, most of the population develops immunity, and adult infection is rare. In countries with a low incidence of infection, such as the United States, immunity to HAV is less common, and the disease is more likely to affect adults, in whom symptoms are common and include fever, malaise, jaundice, and abdominal discomfort, with rare cases of acute liver failure (for which chronic liver disease is considered a risk factor).4 The case-fatality rate for HAV infection is 0.3% to 0.6% overall but may be as high as 1.8% among persons older than 50 years.5
Andersson KL, Friedman LS. Hepatitis A: A Traveling Target: Comment on “The Evolving Epidemiology of Hepatitis A in the United States”. Arch Intern Med. 2010;170(20):1818–1819. doi:10.1001/archinternmed.2010.412
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