Viral hepatitis

Hepatitis A and hepatitis B are distinguished clinically by differences in onset and serologically by the presence of hepatitis A antigen or of any one of at least three hepatitis B antigens on the virus particle. At present, hepatitis non-A, non-B can be diagnosed only by exclusion of the other two types. Clinically it resembles hepatitis B. Hepatitis A is most often contracted through the fecal-oral route, and preschool children are at particular risk. Hepatitis B usually is transmitted by parenteral inoculation of virus-containing material. Transmission is now known to occur venereally as well. Since all blood donors now are screened for hepatitis B surface antigen, the cases of transfusion-associated hepatitis that do occur are caused mainly by non-A, non-B virus(es).