Hepatitis B: transmission by sexual contact and needle sharing.

In the Western world most cases of hepatitis B virus (HBV) infection are acquired through sexual intercourse and through needle sharing by intravenous drug users (IVDU). The major risk factors for HBV infection in homosexual men include the number of sex partners and receptive anal intercourse. In heterosexuals, this risk also rises with an increasing number of sex partners. IVDU consistently show the highest HBV infection rates in Europe and North America, presently accounting for 25 to 50% of all hepatitis B cases. Infection with the human immunodeficiency virus affects the course of HBV infection as well as the immunological response to hepatitis B vaccines. Thus, in the industrialized world, interventions against HBV infection should primarily be targeted to homosexual men, heterosexuals with multiple partners, and IVDU.