Changing epidemiology and clinical aspects of hepatitis A.

The picornavirus responsible for hepatitis A is no longer thought directly cytopathic; it is probable that pathogenesis is dependent on T-cell mediation. Although well known to cause a generally milder illness in young children, it is now clear that the severity of hepatitis A continues to increase steadily with increasing age through adulthood also. Earlier and controversial reports of relapsing hepatitis A are now better supported by investigatory data. Cyclic epidemics are becoming less apparent in the developed world, where particular groups, such as intravenous drug abusers and those in contact with children, account for an increasing proportion of cases. Endemicity is gradually being overcome in developing countries, an effect mainly of improved sanitation, and it has been shown that hepatitis A may disappear entirely from isolated communities.