Hepatitis B virus. Update on the spectrum of clinical infections and on prophylaxis.

Knowledge about hepatitis B virus (HBV) has expanded vastly over the past 20 years, elucidating not only the spectrum of clinical illnesses it causes but also its biologic characteristics. HBV is an important cause of both acute and chronic liver disease in the United States. The most serious outcome of hepatitis B infection is chronic liver disease, which can range from chronic hepatitis eventuating in cirrhosis to primary hepatocellular carcinoma. Molecular biologic studies have shown that HBV-DNA can be integrated into the genome of hepatocytes. This integration may be part of the natural history of chronic hepatitis B infection and may transform normal hepatocytes into neoplastic cells. Immunization with hepatitis B vaccine (Heptavax-B) of persons at high or intermediate risk is an essential means for preventing transmission of hepatitis B. Use of the vaccine after recent exposure to hepatitis B breaks the chain of transmission--an exciting capability. Postexposure immunization of neonates born of HBsAg-positive mothers is particularly important in preventing vertical, or perinatal, transmission of infection.