Trends in HIV Incidence Among Young Adults in the United States

CONTEXT: Behaviors that result in potential exposure to human immunodeficiency virus (HIV) usually begin in adolescence or young adulthood, but trends in HIV incidence in young people remain unclear. OBJECTIVE: To estimate trends in HIV incidence in teenagers and young adults. DESIGN AND SETTING: Back-calculation of past HIV incidence in persons born between 1960 and 1974 using US national acquired immunodeficiency syndrome (AIDS) incidence data and estimates of the distribution of times between HIV infection and AIDS. MAIN OUTCOME MEASURES: Incidence and prevalence of HIV in 1988 and 1993 in persons aged 20 and 25 years, respectively, in each of those years. RESULTS: As of January 1993, about 22000 men and 11000 women aged 18 to 22 years were living with HIV infection in the United States. Homosexual contact was the leading route of infection among young men. Heterosexual contact was the leading route of infection among young women. The HIV incidence attributed to homosexual contact or injection drug use decreased among persons aged 20 and 25 years between 1988 and 1993, but HIV incidence attributed to heterosexual contact was stable or increasing. Notably, in men aged 20 and 25 years, HIV prevalence declined by about 50% in white men but was relatively stable in black and Hispanic men. In contrast, HIV prevalence in women aged 20 and 25 years rose by 36% and 45%, respectively, because of increasing heterosexual transmission. Overall, HIV prevalence in persons aged 20 and 25 years declined by only 14% between 1988 and 1993. CONCLUSIONS: In young persons, HIV incidence in homosexual men and injection drug users was slowing by 1993; this favorable trend was offset by increasing heterosexual transmission, especially in minorities.