Which is the average infection rate of STDs via oral sex?

Question

I recently opened this question in biology.stackexchange.com and from comments it looks like it's better posted in this community (which I agree) so I'm posting it here again:

I'd like to know an approximate rate for the most common ones when giving/receiving oral sex. What I find is just pages that say that infection is possible but those pages don't go into too much detail about how possible it is.

The only study I have found more precise is one that estimates that the risk of contracting HIV by oral sex is pretty low, but that even that is not clear.

I believe it shouldn't be too common to get infected by an STD this way, but maybe my hypothesis is wrong.

Finding that rate for every possible STD could be a too demanding job, so it's enough for me finding the average rate for the most common STDs.

Answer 1

Probably the best evidence around this is for HIV, which is neatly summarised in table 2 of the BASHH (British Association for Sexual Health and HIV) guidelines, where the risk for insertive or receptive oral sex is <1:10000, based on a partner with confirmed HIV and not on any antiretroviral treatment.

Chlamydia, Syphilis, Gonorrhoea, Herpes, and HPV are all documented as being able to spread via oral sex. Precise numbers seem hard to find, no doubt in part as controlled trials would be unethical, so the available information is retrospective and based on recall and disclosure of sexual exposure, and ability to contact trace.

Urogential Chlamydia and Gonorrhoea have been found at similar rates in those only reporting receiving oral sex as in those with insertive anal sex. It is possible that this reflect different prevalence in the source patients, but does suggest that the transmission risk is broadly similar from oral sex as from anal sex. Other studies also show this route to be an independent risk factor for those infections, so the risk is non-negligible.

The odds ratio for testing positive for oral HPV is strongly associated with frequency of oral sex, again suggesting that there is a clinically significant risk of transmission via this route, although again precise risk per exposure isn't readily available.