[Question #13579] HIV and oral sex

1 months ago

Dear doctors,

I understand you phrase the risk as "extremely low", "for all practical purposes as nearly zero" for HIV tranmission via receptive oral sex.

I've also read a lot online from CDC, Catie.ca, Deutsche AIDS-Hilfe, AIDS-Hilfe Schweiz(official German and Swiss agency respectively ). They all state things such "extremely low", "almost no chance if partner doesn't ejaculate" (links - https://www.catie.ca/hiv transmission, https://www.cdc.gov/hiv/causes/index.html, https://www.aidshilfe.de/en/safer-sex-oral-sex, https://aids.ch/en/knowledge/hiv/transmission/).

I want to ask two things:

- Do you agree with public health messaging that what you classify as "extremely low risk" could by many of them be classified as "practically no risk", "negligible risk".

- If Partner A is HIV positive, untreated, would the risk of HIV transmission to Partner B during a single episode of 10 seconds oral sex be easily less than 1 in 100 000? My reasoning is: Baseline risk is 1 in 10000, the brevity of such exposure and no ejaculation further decreases the risk. I understand no clinical trials have been done on this.

H. Hunter Handsfield, MD

1 months ago

Welcome back to the forum.

You correctly summarize the facts -- the very low risk of HIV from oral sex and the agreement of various expert agencies.

"- Do you agree with public health messaging that what you classify as "extremely low risk" could by many of them be classified as "practically no risk", "negligible risk". Yes -- and this is pretty much what most experts and agencies do routine. Do not assume or look for differences between such statements as "extremely low", practically no risk,", negligible risk", and so on. There are no differences between them.

As for your partner A and B scenario, there simply are no data to allow such precise estimates. The often quoted risks of one chance in 10,000 (for penile to oral transmission) and one in 20,000 (for oral to penis) are extremely rough. I'd be OK with something like one chance in 100,000 (i.e. tenfold lower risk) in absence of ejaculation in the mouth. No clinical trials have been done on ANY quantitative risks of HIV transmission. All esimtates are based on surveys of people about how they thought the likely became infected and are very rough estimates at best. W/hat's more certain is that the busiest HIV/AIDS clinics rarely if ever see patients whose only possible exposures to HIV were oral sex.

Perhaps the best way for you to look at all this is to not obsess about numbers and know that you could have the kinds of exposures you have described in your two questions every day for your entire life and expect to never get HIV.

I hope these comments help you move on without worry. Let me know if anything isn't clear.

HHH, MD

---

1 months ago

Dear doctor Handsfield,

many thanks for your reply.

I understand your point regarding clinical trials. Professionally, I come from a pharmaceutical sponsor side so I can see why clinical trials cannot be carried out here the same way one could perform a clinical trial in other therapeutic areas(ethical considerations, patient recruitment etc..)

Your answers are very thorough and I wanted to use this opportunity to thank both you and Dr. Hook for your expertise and all the work you do.

H. Hunter Handsfield, MD

1 months ago

Thanks for the thanks. I'm glad to have helped.---

1 months ago

Dear Dr. Handsfield,

I've noticed I have one more follow up remaining. I understand I shouldn't obsess about numbers and I understand that the risk in this context is practically non-existent. I just wanted to doublecheck my logic - If three acts of receptive oral sex occur, with baseline risk of 1 in 100 000 then the total cumulative risk with three different partners of unknown HIV status would be around 1 in 1 million? My math is: Assuming 15% prevalence of untreated HIV in a particular population; three acts with a baseline risk of 100 000 would give a combined risk of around 1 in 1 million? (population baseline risk x per act baseline risk)

Many thanks for your reply in advance and thank you for all the work you do.

H. Hunter Handsfield, MD

1 months ago

Your math seems to be backwards. Three exposure in theory triples the chance of infection compared with one exposure; you have divided 1 in 100,000 by three instead of multiplying. The guesstimated baseline risk of penile to oral transmission is one in 10,000 not 100,000, so three exposures to partners with untreated HIV in principle makes the risk 1 chance in 3,300. If we accept your 15% guess about the proportion of such partners who indeed have untreated HIV, then 3300 divided by 0.15 gives one chance in 22,000 you would be infected. I would consider that zero for all practical purposes.

All these numbers are exceedingly rough, little more than estimated guesswork -- so don't put too much faith in them. It's more important to know that the vast majority of men with sexual lifestyles along these lines probably could give BJs to a new male partner everyday for life and never acquire HIV. And of course you can lower the chance still further by discussing HIV status with partners before sex -- and deferring sex with the small minority who are HIV positive and untreated -- knowing that most people are truthful when asked directly about HIV status.

As you understand, that completes the two follow-up comments and replies included with each question and so ends this thread. I hope the discussion has been helpful. Best wishes and stay safe.

---