Changes in AIDS incidence trends in the United States.

Estimating the current prevalence of human immunodeficiency virus (HIV) and projecting the future incidence of AIDS require that trends in incidence be analyzed and interpreted. We analyzed AIDS incidence trends in the United States by exposure category and selected demographic factors. In 1987, the trend in United States AIDS incidence changed as growth in the number of cases diagnosed per quarter began to decline. The slowing in growth is due in large part to a plateau in quarterly incidence in men who have sex with men in the New York City, San Francisco, and Los Angeles metropolitan statistical areas (MSAs), and in injecting drug users in the New York City MSA and New Jersey. Incidence has also reached a plateau in both adult/adolescent and pediatric blood and blood product recipients. Quarterly U.S. AIDS incidence was roughly constant during 1990, but appears to have increased to a higher level during the first half of 1991. The variation in incidence trends among subgroups suggests that several factors have affected the trend in total incidence and that the burden of severe symptomatic HIV disease may be shifting.