I am an HIV neg, HSV2 pos gay man who engaged in anal intercourse for the first time in about ten years today after being in a long relationship with a partner who didn't enjoy anal. 

The person I had sex with said he was negative. We had unprotected oral and protected anal--we both bottomed and topped each other.

When I got home I started to get a little worried. (Like I said, it has been so long since I've done anything riskier than oral) and I went to the CDC website to reassure myself that everything was cool. As you probably know, CDC lists the per exposure risk with an infected parter at 138 out of 10,000 for receptive anal. Here's what got me confused and why I am writing: There was an asterisk below the exposure risk chart that said:

Good online research, finding the main CDC published study estimating per-exposure HIV risks for specific sexual practices. That's the one that is the basis of our comments and advice on the subject. 138 per 10,000 is equivalent to around once per 70 exposures. However, CDC has other published data as well, using different statistical methods and/or previously published literature, and that estimate for receptive anal with an infected partner as 50 per 10,000, or once every 200 exposures. In any case, it's the highest HIV risk of all types of sexual exposure. However, it still means that the large majority of such exposures do not result in virus transmission. And today the figures would have to be modified to take into account that many (most?) HIV infected MSM are on effective antiviral treatment, which virtually eliminates the potential for transmission by any sexual exposure. And all this is pertinent only if your new partner has untreated HIV -- which is unlikely, as you point out yourself. (In general, people do not lie about HIV status in such situations.)

As for condoms, you are exactly right:  a correctly used condom that does not break is 100% protection, or very close to 100%. Estimates of lower protection levels generally are based on real-world usage over time. For example, we know that couple who use condoms as their only contraceptive have a 90% reduction in pregnancy rate -- not bad, but nowhere near the virtual 100% with birth control pills. Similarly, regular condom users have well under 100% protection against HIV and other STIs. It's the difference between biological effectiveness (no virus, bacteria, sperm, or genital fluids can pass through intact latex) and real world use, reflecting untruthful reporting, forgetfulness (drugs, alcohol, etc), and breakage -- with breakage more common for anal than vaginal sex.

Your split lip probably didn't enhance your risk at all. Healing wounds are rarely if ever a source of HIV, even when exposed to infected blood or fluids. Performing oral sex on infected (and untreated) partners has an estimated risk of one in 10,000, which is equivalent to giving BJs to infected men once daily for 27 years before infection might be likely; and of course at any point in time, lots of people have canker sores, split lips, bite injuries of their cheeks, etc, etc -- and still don't get HIV.

Of course you could contact your partner with these concerns. He might be willing to be retested to reassure you; and maybe you would find he is just as nervous about your HIV status as you are about his. You could offer to retest yourself at the same time.

In the meantime, I really wouldn't be worried. But if you remain nervous and your partner isn't retested, you're of course free to have an AgAb (4th generation) HIV blood test in a few weeks; you can expect negative results.

Finally, you don't mention other STIs like gonorrhea, chlamydia and syphilis, all of which are higher risk than HIV. Absence of symptoms is reasonably good reassurance about all of them, but only testing can tell for sure. However, in general it doesn't make a lot of sense to automatically test for any of these, or HIV, after any single exposure. A wiser strategy is periodic testing, perhaps every 6 months or a year, depending on frequency of sex with new or at-risk partners. And, if such exposures in fact are quite frequent, pre-exposure prophylaxis (PrEP), i.e. anti-HIV drugs taken for a couple of days before sex.

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

HHH, MD

Thank you so much for your response! My only other question would be: Would you reccomend Post Exposure Profylaxis, but I'm guessing your answer is that I don't, despite the bleeding lip coming in contact with pre-cum. Is pre-cum even that infectious? I'm unclear on that. I'm assuming it is less so that semen. 

And that you for your thoughts regarding STI's more generally. I definitely intend to make a habit of  testing every 6 months, or testing right away if I have an obvious symptom. 

Thank you for your time and expertise!

Good testing plan!