Hepatitis B: diagnosis and treatment.

The hepatitis B virus (HBV), a member of the Hepadnaviridae family, was discovered 30 years ago. Since that time, clinical and basic research has led to a clear understanding of the epidemiology and natural history of infection and the pathogenesis of the resulting liver injury. Physicians are now able to accurately diagnose acute and chronic infection, though our understanding of viral quantitation and its impact on disease course and treatment response is evolving. Hepatitis B must now be considered a preventable disease, since acute infection can be effectively prevented by either passive or active immunization. However, when acute infection does occur, it evolves into chronic hepatitis or a chronic infectious carrier state in a variable proportion of cases, depending on the age and underlying immune competence of the patient. Chronic infection can be treated, though the effectiveness of available antiviral and immunomodulatory agents is less than complete. Finally, variants of the HBV are being recognized, and coinfection with the defective viroid known as hepatitis D (formerly delta agent) has been described.