Estimated HIV Transmission Risk per Exposure| Type of exposure | Estimated risk HIV transmission per exposure |
| Receptive anal intercourse | ≤ 3.0 percent (1/125 to 1/31) (DeGruttola and others 1989) |
| Receptive vaginal intercourse | ≤ 0.1 percent (1/2,000 to 1/667) (Mastro and others 1994; Wiley, Herschkorn, and Padian 1989) |
| Insertive vaginal or anal intercourse | ≤ 0.1 percent (1/3,333 to 1/1,111) (Nagachinta and others 1997; Peterman and others 1988) |
| Needlestick injury | = 0.3 percent (1/313) (Henderson and others 1990) |
| Use of contaminated injecting drug equipment | = 0.6 percent (1/149) (Kaplan and Heimer 1992) |
| Mucous membrane | = 0.1 percent (1/1,111) (Ippolito, Puro, and De Carli 1993) |
