WITH GREAT FANFARE, federal public health officials announced in 1997 that prevention efforts were finally paying off, for AIDS deaths had started to decline. At the same time, however, they noted that at least forty thousand new HIV infections occur in the United States every year. A small percentage of these infections are present at birth or occur through blood transfusions. However, the vast majority of people who contract the AIDS virus do so by engaging in risky behavior. Sixty percent of the 476,899 AIDS cases reported to the Centers for Disease Control as of June 1995 resulted from sexual contact. Thirty-two percent resulted from shared needles. These numbers illustrate the difficulty of preventing an infectious disease that is, as one group of researchers states, "largely a disease of behaviors."

Without a preventive vaccine, and with little hope of seeing one...