Hiv female to male transmission?

my friend had unprotected vaginal intercourse with a woman who is HIV positive. neither of them had any open soars of cuts. the woman is on Combivor (an antiretroviral drug)

what are his risks?

We know that based on biology/anatomy it is easier for an HIV+ man to give HIV to a woman (penile-vaginal sex) than it is for an HIV+ woman to give HIV to a man (penile-vaginal sex).

Cuts are not required for HIV to enter the male. Body fluids (blood, vaginal secretions, rectal secretions) can come into contact with the mucosal membrane of the urethra (pee hole) or, if the man is uncircumcised, the body fluid can come into contact with the mucosal-like skin of the foreskin. It is possible for HIV to cross into the blood stream without cuts/tears.

The fact that the woman who was HIV+ was also on treatment, most likely lessens the chances that transmission occurred. We know that, in general, the lower a person's viral load, the less infectious they are. A person on treatment (assuming they are taking it correctly and it is working) usually has a very low if not undetectable viral load making transmission less likely (but still possible).

So, unprotected vaginal sex is considered a high risk activity so the risk of HIV transmission is real. There are some factors that make transmission a bit less likely in this case, but bottom line:

HIV transmission could have occurred. Your friend needs to be tested immediately. and tested again at least 3 months after the exposure.

There is always a risk. Things like her viral load would play a big part as well. If her viral load is low the risk is lower, if it's high, his risk is much higher. The odds are in his favor that nothing happened, but I would encourage a HIV test NOW and then again in 3 months.

the chance is always there that you get it unprotected.