By 1985 the acquired immunodeficiency syndrome (AIDS) had been recognized as an
epidemic of major public health importance and the primary etiologic agent, human
immunodeficiency virus, type 1 (HIV-1), had been identified. At that time, major studies had
started to characterize the natural history of HIV-1 infection among homosexual/bisexual
men (Kaslow et al. 1987; Winklestein et al. 1987; Schechter et al. 1985), who accounted for
about 75 percent of the cases of AIDS (Centers for Disease Control 1986). However, the …

To identify risk factors for infection with the human immunodeficiency virus (HIV) and for
progression to the acquired immunodeficiency syndrome (AIDS) among intravenous drug
users, we established a cohort in Baltimore Maryland in 1988–1989. Intravenous drug users
were recruited by extensive community outreach to undergo interview and confidential HIV
testing in a special study site. During 13 months of recruitment, 2,921 intravenous drug users
were enrolled of whome 24 percent were HIV seropositive; 90 percent returned to receive …