One month ago,

I anally penetrated a girl, an erotic masseuse in Central America, with my underwear on.

I thought it was a type of erotic game, but it lasted a long time, ten to fifteen minutes, it wasn't rough at all.

Afterwards I felt like I had put myself at risk, and I went to a medical clinic and they gave me pep (only truvada).

Could you please answer my following questions:

1. Did this situation put me at risk of contracting HIV or another STD?

2. Just taking truvadas is enough for PEP, they shouldn't have given me any other medication besides truvada.

3. I could have infected my partner if I had contact with her three days after this incident. Intercourse with a condom, but perhaps some casual contact with precum.

4. All my tests have come back negative, when I finish pep, I have to take another test.

I sincerely appreciate your help!

As you might imagine, there are no data on the likelihood of transmission of HIV or other STDs through clothing. We generally say that logic dictates virus/bacteria transmission cannot occur; cloth fibers almost certainly are efficient barriers that trap both fluids and bacteria and viruses. And we are unaware of any cases, ever, in whom such contact was the only possible source for someone's HIV, gonorrhea, chlamydia, herpes, syphilis, etc. So at least we can be confident that the risk is extremely low.

That said, almost all such reports on this forum come from questioners with very brief contact; this is the first I know about in which anal or vaginal penetration occurred for anything like 10-15 minutes with underwear or other clothing covering the penis. Assuming "underwear" means a thin, single-layered garment, I can image there was opportunity for HIV/STD transmission. Undoubtedly it would be lower risk than for entirely unprotected penetration, but perhaps not risk free.

In judging your risk, it would also be helpful to know a bit more about your "erotic masseuse" partner. Clearly she is a sex worker, but do you have any idea how often such contact might occur with her massage clients? Does she provide other sex services, like unprotected vaginal penetration? However, even if she does these things, most female sex workers don't have HIV or other active, transmissible STDs. And when a female has untreated HIV, even with completely unprotected anal sex, the average risk to her male partner (from a single exposure) is around one chance in a thousand. In other words, you were at pretty low risk of HIV (and probably other STDs) even if your underwear were not a factor.

Those comments get a start on your numbered questions, but to be explicit:

1. See comments above. As a guesstimate, I would put the chance you would have caught HIV, without PEP, at one chance in many thousands, maybe as low as one in a million.

2. As that implies, I would have considered this event as not requiring PEP. However, the doctor or clinic you saw might have more experience in HIV epidemiology in the local area. So I'm not criticizing your starting PEP. In any case, Truvada alone is highly effective; adding another anti-HIV drug only slightly improves effectiveness. 

3. HIV is not transmissible sooner than 7-8 days after catching it. Your partner is not at risk for HIV on account of a single exposure 3 days later, especially since it was condom protected.

4. Most experts advise that accurate final testing following PEP must be done 6 weeks after the last dose of drug. But follow your doctor's or clinic's advice on this.

I hope these comments are helpful. Let me know if anything isn't clear.

HHH, MD