Hepatitis A is an acute, necroinflammatory disease of the liver which results.from infection by the hepatitis A virus (HAV). The mean incubation period is approximately 30 days. Although the disease is usually self-limited, the severity of illness is age-dependent. In children, hepatitis A is usually asymptomatic, while in adults, symptomatic infection is characteristic and jaundice is common. Fulminant hepatitis A is rare and is also age-dependent. The onset of hepatitis A is often abrupt and characteristic prodromal symptoms are followed, within a few days to a week, by dark urine and jaundice. Mild to moderate tenderness over an enlarged liver is usually detected. Serum alanine and aspartate aminotransferase levels usually both rise rapidly during the prodromal period, reach peak levels and then decrease by almost-equal-to 75% per week. Serum bilirubin concentrations reach peak levels later and decline less rapidly than serum aminotransferases. Nonetheless, the period of jaundice persists for < 2 weeks in almost-equal-to 85% of cases. Nearly all adult patients with clinically apparent disease experience complete clinical recovery with restoration of normal serum bilirubin and aminotransferase values by 6 months. Relapses and prolonged cholestasis are unusual manifestations of hepatitis A, and even in these circumstances, recovery is the rule and chronic hepatitis is not seen. The diagnosis of hepatitis A requires the detection of immunoglobulin M antibody to HAV in a patient who presents with, or has recently had, clinical features of hepatitis (icteric or anicteric disease) or in an individual with inapparent, asymptomatic infection in whom serum aminotransferase elevations may be detected. In occasional individuals monitored because of exposure to the disease, serological confirmation of acute HAV infection may occur in the absence of detectable aminotransferase elevations.
