Table 1 Logical formulas for risk factor definitions

Heterosexual

heterosexual exposure (regardless of having homosexual exposure)^a OR having one or more partners of the opposite sex^a OR self-reporting being infected through heterosexual exposure

High-risk heterosexual

having heterosexual exposure (defined above) AND [having had a sexual partner who injects drugs^a OR having had heterosexual contact with an HIV-positive person^a OR giving or receiving money or drugs for sex^a OR [having had a sexual partner who was bisexual^a AND being female]]

Injecting drug use

injecting illicit drugs at least once^a OR self-reporting injecting drug use as the most likely mode of HIV transmission

Homosexual

being male AND [having sexual contact with men at the present time OR having one or more male sexual partners^a OR having a sexual partner of the same sex^a OR having homosexual contact with an HIV-positive person^a OR self-reporting homosexual exposure as the most likely mode of HIV transmission]

Nosocomial

having had blood or blood product transfusion^a OR having had organ or tissue transplantation^a OR having had in vitro fertilization^a OR self-reporting being infected through medical procedures

Skin penetration

reporting intentional skin penetration (tattoo, scarring, or other practices)^a OR having been exposed to another person’s blood through damaged skin or mucosa^a OR reporting being infected in an occupational or non-occupational accident with skin penetration

Sexually transmitted infections

self-report on having HBV OR gonorrhea OR syphilis OR genital herpes OR proctitis OR other STI at any time before finding out about HIV-positive status

Exposure to HCV

positive test for anti-HCV antibodies

Exposure to HBV

positive test for HBsAg OR positive test for AntiHBc antibody