The first evidence of the AIDS epidemic in the United States appeared in groups of individuals who shared a common exposure risk. Sexually active homosexual men were among the first to present with manifestations of HIV disease, followed by recipients of blood or blood products, then injection drug users, and ultimately children of mothers at risk. Virtually all cases of HIV transmission can be attributed to these exposure categories.

In the United States, HIV-related illness and death historically have had a tremendous impact on men who have sex with men (MSM). Even though the toll of the epidemic among injection drug users (IDUs) and heterosexuals has increased during the last decade, MSM continue to account for the largest number of people reported with AIDS each year. In 1999 alone, 15,464 AIDS cases were reported among MSM, compared with 10,138 among IDUs and 7,139 among men and women who acquired HIV heterosexually.

Past experiences in planning, implementing, and evaluating efforts to stem the U.S. epidemic have clearly shown that preventing HIV infection depends on two equally important factors–studying and implementing biomedical interventions to thwart the virus, and influencing millions of individuals in diverse populations to adopt or maintain safe behaviors. Comprehensive, sustained prevention activities offer the best hope for slowing the epidemic’s spread.

In the United States, complacency about the need for HIV prevention may be among the strongest barriers communities face as they plan to meet the next century’s prevention needs. The great success that many people, but not all, have had with new highly active therapies (HAART, also known as drug "cocktails") and the resulting decline in the number of newly reported AIDS cases and deaths are indeed good news. The underlying reality, however, is that the HIV epidemic in our country is far from over. This is true not only for the nation, but for the continuing number of HIV-infected individuals who now must face years – perhaps a lifetime – of multiple daily medications, possible unpleasant or severe side effects, and great expense associated with the medicines needed to suppress HIV and prevent opportunistic infections.

The success of HAART may lull people into believing that preventing HIV infection is no longer important. This complacency about the need for prevention adds a new dimension of complexity for both program planners and individuals at risk.