Hepatitis B: the disease.

Hepatitis B virus (HBV) is carried by approximately 300 million people in the world. The natural history of the disease in an individual patient depends on the method by which the infection was acquired, whether perinatal, in childhood, as a result of drug abuse, or in the course of health care work. Other important factors determining the course of the disease include an individual's sex and immunological status. Geographic factors also contribute. Changing lifestyles and the use of prophylactic hepatitis B vaccination affect the prevalence in various groups in the community. The clinical course of the disease, possible complications, and a recent classification system for chronic HBsAg carriers are discussed.