Documented male-to-female transmission of HIV-1 after minimal vaginal exposure in the absence of other cofactors for infection.

AIDS cases attributable to heterosexual vaginal intercourse constitute a growing proportion of new AIDS cases in the United States. Major cofactors that possibly increase the efficiency of heterosexual transmission of HIV-1 include genital ulcer disease, multiple sexual exposures, lack of male circumcision, and primary and advanced stages of HIV-1 disease. I report the case of a 33-year-old woman who was recently infected with HIV-1 after one to three nontraumatic episodes of vaginal intercourse with a healthy-appearing, HIV-1-infected, bisexual man. An investigation of her exposure history revealed the precise time frame during which infection occurred. The patient developed a primary HIV-1-infection syndrome and became seropositive for HIV-1 within eight weeks of her last sexual contact with the infected man. An epidemiological and laboratory evaluation of the index patient and her sexual partner identified only one risk factor for enhanced HIV-1 transmission: the patient's use of oral contraceptives. Her partner was immunologically intact, HIV-1 antigen negative, and circumcised. Both of the individuals were from Minnesota, as were their recent sexual partners. This case illustrates that HIV-1 infection by vaginal intercourse can occur in the absence of the major risk factors believed to increase the efficiency of transmission. Even in a low HIV-1 prevalence area like Minnesota, efforts to promote awareness of HIV-1 status, abstinence, non-penetrative sex, or barrier protection need to be expanded and the behaviors adopted by sexually active persons if HIV-1 transmission is to be minimized.