Per-contact risk of human immunodeficiency virus transmission between male sexual partners

Am J Epidemiol. 1999 Aug 1;150(3):306-11. doi: 10.1093/oxfordjournals.aje.a010003.


The risk of human immunodeficiency virus (HIV) transmission from various types of homosexual contact, including oral sex, is of biologic, epidemiologic, and public health importance. The per-contact risk of acquiring HIV infection from specific acts was estimated in a prospective cohort study of 2,189 high-risk homosexual and bisexual men, conducted in San Francisco, California; Denver, Colorado; and Chicago, Illinois, in 1992-1994. During 2,633 person-years of follow-up, 60 seroconversions were observed. The estimated per-contact risk of acquiring HIV from unprotected receptive anal intercourse (URA) was 0.82 percent (95% confidence interval: 0.24, 2.76 percent) when the partner was known to be HIV+ and 0.27 percent (95% confidence interval: 0.06, 0.49 percent) when partners of unknown serostatus were included. There was heterogeneity in per-contact risk, with nine seroconversions occurring after only one or two episodes of URA. The per-contact risk associated with unprotected insertive anal and receptive oral sex with HIV-positive or unknown serostatus partners was 0.06 and 0.04 percent, respectively. URA accounted for only 15 percent of all reported sexual activity by seroconverters. As lower-risk practices become more common, they may play a larger role in propagating the epidemic and should also be addressed by interventions targeting high-risk homosexual and bisexual men.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Cohort Studies
  • Condoms / statistics & numerical data
  • Disease Transmission, Infectious / statistics & numerical data*
  • HIV Infections / epidemiology
  • HIV Infections / transmission*
  • HIV Seropositivity
  • HIV Seroprevalence
  • Homosexuality, Male / statistics & numerical data*
  • Humans
  • Male
  • Risk Factors
  • Sexual Behavior / statistics & numerical data*
  • Surveys and Questionnaires
  • United States / epidemiology