Table 1: Bernoulli formula, estimated risk parameters, and self-reported behaviors used to create composite HIV risk outcome measure (HIVRISK).
 Bernoulli mathematical formula HIVRISK = Estimated HIV risk parameters Base estimates Source : probability that primary male sex partner is HIV infected † : probability that a secondary sex partner is HIV infected 0.15 ‡ : probability that an injection partner is HIV infected 0.25 ‡ : per contact probability of HIV transmission (infectivity) for anal sex .017 [43, 44] : per contact HIV transmission for male-to-female vaginal sex .0008 [43] : per act HIV transmission for receptive syringe sharing .0074 [45, 46] : condom failure rate .10 [44] Measured self-reported risk behaviors mvu: number of acts of condom unprotected vaginal intercourse with primary male partner mvp: number of acts of condom protected vaginal intercourse with primary male partner mau: number of acts of condom unprotected anal intercourse with primary male partner map: number of acts of condom protected anal intercourse with primary male partner mij: number of times receptive syringe sharing with primary male partner svu: number of acts of condom unprotected vaginal intercourse with secondary sex partner svp: number of acts of condom protected vaginal intercourse with secondary sex partner sau: number of acts of condom unprotected anal intercourse with secondary sex partner sap: number of acts of condom protected anal intercourse with secondary sex partner sij: number of times receptive syringe sharing with secondary partner sv: number of secondary vaginal sex partners sa: number of secondary anal sex partners sj: number of secondary injection partners
A represents HIV risk from a primary male partner; B is HIV risk from a secondary sex partner; C is HIV risk from a secondary injection partner.
Based on self-reported HIV status of male partner: self-reported HIV positive = 1.0; self-reported HIV negative/unaware and IDU = 0.15; self-reported HIV negative/unaware and non-IDU = .05.
Based on unpublished data on HIV prevalence among IDU and non-IDU men in Harlem and South Bronx, NY, USA.