Hepatitis A.
The introduction of hepatitis A vaccines in 1995 led to a drop in the number of reported cases of hepatitis A and a shift to a higher percentage of cases occurring in older age groups. The hepatitis A virus survives for extended periods in the environment. Transmission primarily is fecal-oral, although there have been rare instances of transmission through blood products. The virus appears sporadically and is spread by close personal contact, with occasional food-borne outbreaks. Older persons infected by the virus usually develop a symptomatic infection with abrupt onset, fever, and jaundice lasting two months. Children usually have an asymptomatic infection and rarely develop jaundice. Laboratory diagnosis is made by detection of antihepatitis A virus immunoglobulin M in serum. Ten to 20 percent of symptomatic patients experience a prolonged or relapsing course of illness, but chronic infection has not been reported. Fulminant infection occurs in less than 1 percent of patients and can result in emergent liver transplant or death. Prevention starts with thorough handwashing and careful food handling. Prompt disease reporting, the identification of exposed persons, and expeditious administration of immune globulin prevent secondary transmission of the disease. Physicians should consider routine vaccination of children 12 to 23 months of age based on recommendations from the Centers for Disease Control and Prevention. Vaccination for children two years or older and adults should be included in routine preventive care for those at increased risk of contracting the disease (e.g., travelers to certain countries, men who have sex with men, drug abusers, recipients of clotting factor replacement) and for persons with chronic liver disease.