The epidemiology of human immunodeficiency virus infection and acquired immunodeficiency syndrome in the United States.

As of October 1989, there were more than 112,000 documented cases of AIDS and more than 1 million Americans were thought to be infected with HIV. Three primary routes of HIV transmission have been defined: sexual contact, parenteral exposure, and perinatal transmission. Epidemiologic surveillance studies provide important information about trends in HIV infection and AIDS among groups recognized to be at increased risk, various demographic subgroups, and the general population. As of this writing, the majority of reported cases have occurred among homosexual or bisexual men. However, a growing risk category involves intravenous drug users, as well as their sexual partners and their children.