Viral Hepatitis

Epidemiological studies of viral hepatitis in the late 1930s and early 1940s defined two clinical syndromes. The first, infectious hepatitis, described epidemic jaundice occurring in crowded living areas and spread by the fecal-oral route. The incubation period was short, three to six weeks, and the prodrome was abrupt. The second form, serum hepatitis, described sporadic cases occurring predominately after blood transfusion and spread by the parenteral route. The incubation period was longer than that for infectious hepatitis, up to 6 months, and the onset of clinical illness was frequently insidious or inapparent. Chronic liver disease was seen only with serum hepatitis, while fulminant liver disease was seen in both varieties, although more commonly with serum hepatitis. It is clear now that infectious hepatitis and serum hepatitis describe hepatitis A virus and hepatitis B virus infection, respectively. Viral hepatitis not caused by hepatitis A or B virus or known viruses causing hepatic damage (eg, Toxoplasma, CMV, EB virus, herpes, adenovirus), has recently been described and designated as nonA, nonB hepatitis. Recent developments clarifying the populations at risk for infection, the potential sources for infection, the clinical stages of viral hepatitis, and the role for immunoprophylaxis (vaccine and gamma globulin), in each of these three major viral hepatitides will be described.