Over the past decade, limited attention has been paid to the human immunodeficiency virus (HIV) epidemic in the United States. The global epidemic—particularly the epidemic in sub-Saharan Africa, where approximately two thirds of the world’s population living with AIDS resides—has rightfully received most of the focus. Meanwhile, however, the prevalence of HIV infection within some US populations now rivals that in some sub-Saharan African countries (see graph). For example, more than 1 in 30 adults in Washington, DC, are HIV-infected—a prevalence higher than that reported in Ethiopia, Nigeria, or Rwanda. 1 Certain US subpopulations are particularly hard hit. In New York City, 1 in 40 blacks, 1 in 10 men who have sex with men, and 1 in 8 injection-drug users are HIV-infected, as are 1 in 16 black men in Washington, DC 2 In several US urban areas, the HIV prevalence among men who have sex with men is as high as 30% 3—as compared with a general-population prevalence of 7.8% in Kenya and 16.9% in South Africa.

During the first two decades of the epidemic, remarkable advances in preventing mother-tochild transmission, screening of blood and blood products, and behavior change among men who have sex with men resulted in significant decreases in new HIV infections in the United States—from approximately 130,000 in 1984 to about 60,000 in 1991. For the past decade, however, progress has been stalled. It had been anticipated that effective antiretroviral therapy, with its suppressive effect on viral replication, would reduce the overall rate of new infections, but this expectation has not been realized. More than half a million Americans became infected with HIV in the past decade, including about 56,000 in the past year. 4 It is estimated that there are now more than 1 million HIV-infected Americans, more than 20% of whom are unaware of their infection.