Hepatitis B viral infection: Part II. Public health aspects.

It is estimated that 200 million people worldwide, including 0.1 percent of the U.S. populations, are carriers of hepatitis B virus. The carrier state is defined as positivity for hepatitis B surface antigen for six or more months without additional features of acute or chronic infection. The risk of spreading hepatitis B virus depends on the infectivity of the carrier, the nature of exposure to the carrier and the susceptibility of the contact. At present, some types of exposure merit prophylaxis with immune globulin. A safe and effective vaccine is currently available and should markedly reduce the incidence of hepatitis B and its chronic sequelae.