OBJECTIVES - This study sought to examine risk factors associated with human immunodeficiency virus type 1 (HIV-1) seroconversion among active-duty men in the US Army.
METHODS - One hundred twenty-eight men with documented HIV-1 seroconversion between 1988 and 1991 were matched to control subjects on demographic variables. Risk factor information was collected for the seroconversion period.
RESULTS - Forty-nine case subjects and no control subjects reported same-gender sex; this includes 34 case subjects who also reported sex with women. Seventy case and 118 control subjects reported no risk factors other than heterosexual intercourse. Among heterosexuals, excess risk was noted for men who had sex with women in risk categories defined by the Centers for Disease Control and Prevention (odds ratio = 10.0; 95% confidence interval = 1.3, 78.1). Significant trends of increasing risk for seroconversion were found with increasing numbers of female partners, nonsteady partners, and partners with whom sex occurred on the first day of acquaintance.
CONCLUSIONS - In this population, the major risk factor for HIV-1 seroconversion was same-gender sex. Among heterosexuals, sex with anonymous or causal partners increased this risk. Intervention programs should emphasize the risk of indiscriminate partner selection in addition to "safe sex" practices.