Update: acquired immunodeficiency syndrome--United States, 1991.

During 1991, state and territorial health departments reported 45,506 cases (17.9 per 100,000 population) of acquired immunodeficiency syndrome (AIDS) to CDC. As in previous years, most cases (52.7%) were attributable to human immunodeficiency virus (HIV) transmission among homosexual/bisexual men. The proportion of cases among these men during 1991 decreased from that in 1990, while the proportions among women and heterosexual men who were injecting-drug users (IDUs) increased, representing nearly one fourth of reported cases in 1991. This report summarizes the characteristics of persons reported with AIDS in 1991 and compares these data with 1990 (Table 1).*