I wanted to confirm some information I received on another forum that cites the experts here (specifically HHH and EWH) to claim that MSM oral sex in all its forms—giving, receiving, swallowing, etc.—is a no risk activity from an HIV point-of-view.   

1) I know the answer can be nuanced, but do the experts here agree with this interpretation?  In other words, from an HIV perspective am I safe to give unprotected oral sex even with swallowing so long as I avoid anal sex altogether?  Is the CDC risk assessment of 1 in 10,000 infections per encounter for the oral partner overly cautious?  For the purposes this discussion, let’s assume I am engaging with casual partners that I don’t know well or sex workers but am asking them about their HIV status before engaging with them.

2) I know that there are risks for other STDs from oral sex like Gonorrhea, Syphilis, HSV, etc.  But is it also true that the risk of infection for the oral partner is considerably lower when only engaging in oral sex? 

I appreciate your feedback on this. There is a lot of confusing information out there. 

We have been misquoted and/or misinterpreted. We do not advise that oral sex is entirely risk free -- at least we try to be careful not to say that in so many words. (Don't count casual comments in passing that might say something like "Don't worry, this didn't put you at risk.") We do point out some scientific facts:  that there has never been a reported, scientifically proved HIV transmisison mouth to penis, or by cunnilingus (oral-vaginal sex) in either direction. There have been a small number of well documented cases of HIV transmitted penis to mouth, i.e. to the receptive (oral) partner in fellatio. We also often cite CDC estimates of the risks, i.e. some of the numbers you mention yourself:  1 chance in 10,000 for the oral partner in fellatio and 1 in 20,000 for the penile partner, if the other participant has HIV. These numbers are equivlent to performing or receiving oral sex with infected men once daily for 27 years before the risk of becoming infected reaches high levels; and daily for 55 years for the penile partner.

Even these estimates may be too high, for two reasons. First, they are based on interviewing HIV infected persons who think they know when and where they were infected, when in fact many of them probably had other risks they didn't divulge. Second, these estimates are more than a decade old, when few infected people were on anti-HIV drugs, which we now know drops the transmission risk to zero or close to it.

1) Those comments address your first question, but to be explicit, if your only sexual exposures with other men are unprotected oral sex, your risk of HIV will be exceedingly low, but not zero. You're the only one who can decide what level of risk you're willing to accept.

2) Some other STDs are much more readily transmitted by oral sex than HIV is. Gonorrhea is the highest risk. (Neisseria gonorrhoae -- the gonococcus, the cause of gonorrhea) is biologically and genetically closely related to several entirely normal pharyngeal (throat) bacteria. This probably explains why it can infect the throat readily -- it finds a relatively hospitable environment. And once there, it probably thrives sufficiently so that there are substantial numbers, sufficient to be transmitted to a partner by oral sex. OTOH, chlamydia can infect the throat but does so much less readily, and there has never been a proved case of chlamydia tranmitted oral to genital. Syphilis is readily transmitted by oral sex (and even by kissing), except that oral involvement with syphilis isn't very common -- but the risk is real among men having sex with other men. HSV1, the cause of oral herpes (cold sores) is readily transmitted by oral sex. Trichomonas and Mycoplasma genitalium are believed to rarely infect the oral cavity, but research is scant and there may be more risk than presently believed. HPV clearly infects the oral cavity, but transmission in the other direction -- mouth to genitals, or by kissing -- appears to be rare.

That said, your statement is correct. Although oral sex certainly can transmit STDs, all in all the risk and frequency of transmission is a lot lower than for unprotected penile-vaginal and penile-anal sex.

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

HHH, MD