Question: what are the chances of getting hiv in one encounter?
Answer: As for anal sex, the most risky sex act in terms of HIV transmission, if an HIV-negative top—the insertive partner—and an HIV-positive bottom have unprotected sex, the chances of the top contracting the virus from a single encounter are 1 in 909 (or 0.11 percent) if he's circumcised and 1 in 161 (or 0.62 percent) if ...