[Question #9282] Syphilis

34 months ago

Hello Doctors.

I am a heterosexual male. 9 days ago I visited a CSW in her apartment (kind of a brothel), in Switzerland. I received unprotected oral sex (fellatio) and protected vaginal sex, and some kissing. The (unwanted) unprotected fellatio lasted approximately 20 seconds untill I stopped her.

Untill now, I have not developed any symptom. However, I am extremely scared of the possibilities I could have contracted syphilis.

The CSW was from Eastern Europe (I don't know however if she lives permanently in Switzerland) and the prestation was quite expensive, about 300 USD. I have read on internet that STDs are more common in people from Eastern Europe.
The yearly incidence of syphilis in Switzerland is 8/ 100000 population. However, based on a study (by Vu, https://smw.ch/article/doi/smw.2020.20357), the prevalence of syphilis among CSW in Switzerland was 5% (all stages). It also scares me that she gave me an unprotected fellatio, so I might think that she does it with some of her clients.

Based on your experience what are the chances I could have contracted syphilis? Could you please give an estimate of the risk? I have read several posts in your forum, and it seems that the chance of orally transmitted syphilis is quite low (even if she was infected), but I am extremely worried anyway. Does the short duration of the act influence the risk of syphilis?

Thank you for your help and service.

H. Hunter Handsfield, MD

34 months ago

Welcome to the forum and thanks for your confidence in our services, and for reading other threads with questions similar to your own.

You've done good research -- you know as much as I do about high rates of syphilis in Eastern Europe, and more than I did about rates in Switzerland. Still, it is rarely useful to translate population-level risks down to the individual level. As just one example that could affect your risk, if your CSW partner left her original home more than a year ago, then even if she has syphilis she acquired while there, probably it is no longer infectious. (Syphilis generally becomes non-transmissible after a year.) Her price also is somewhat reassuring: escorts (expensive female sex workers) typically have low rates of transmissible STIs: they protect their health, use condoms for vaginal or anal sex, have relatively low risk clients (men like you!), and are tested frequently. And among all STIs, syphilis is among the least common in such persons. On the other hand, you describe a somewhat brothel like setting; it conceivable the CSW is controlled by others (pimps etc) and may not always have a free choice in her clients.

As for the sexual exposure itself, it was wise to use a condom; and although syphilis can be transmitted by oral sex, it's rare; and even rarer than otherwise given the brevity of the oral sex exposure, as you suggest yourself. In other words, you have correctly interpreted other comments you found on this forum. All things considered, I think the chance you acquired syphilis was under one chance in thousands; even one chance in a million probably would be too high an estimate.

Another thought that could influence all this: you could consider contacting local (or provincial?) public health. Conceivably you might learn that this particular setting is a hotbed of syphilis or other STIs, or that there are high rates in general in CSWs like your partner. If they advise the risk to be fairly high, you could discuss the possibility of prophylactic treatment with the standard dose of long acting (benzathine) penicillin. Or just visit a local urgent care clinic. If somehow I were in your situation, I would not feel a need for treatment and would not even be tested for syphilis (or any other STI, or HIV) on account of this event. But if these measures would give you more confidence and allow to sleep more soundly, you could consider these options.

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

HHH, MD

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34 months ago

Thank you very much for your reply. It somehow reassures me.

I believe the CSW was independent. She had an announcement on an escort/prostitute website, and I think that that apartment is rented out to different prostitutes in alternation. Given the setting, I might consider her probability to have syphilis quite lower than 5% (this value might be more applicable to street prostitutes, and the study did not differentiate for the stage of syphilis, which might also be latent)?

If I interpret correctly your risk calculation, you consider the chance she had syphilis as 1/100 (or even 1/1000) and the probability of oral to penile transmission (given that she is infectious) as 1/100 (or even 1/1000). Is it reasonable to assume 1/100 (or 1/1000) for the oral transmission probability? These values would give a risk between 1/10.000 to 1/milion, which should be low enough to not be too worried.

Regarding the necessity for a prophylactic treatment, and given this risk estimate, you wouldn't advise me to take it at this stage (unless for emotional reassurance, but not based on the risk level)? You would not be excessively worried about this risk? How long after the potential exposure can the prophylactic treatment be taken? Does it have any side effect?

So to summarize: if you hypothetically were in my situation, you would just wait 3 weeks and lookout for symptoms (sores), and in case take a test and treatment thereafter? (I guess this would still be safe and I wouldn't risk permanent health issues?). And you wouldn't be very worried, as syphilis is quite rarely transmitted by oral sex?

Thanks again for the very professional advices!

H. Hunter Handsfield, MD

34 months ago

Your figures are reasonable, but probably overestimate your risk of syphilis. Correct that I suggest consideration of treatment strictly for reassurance, not based on risk level. If you go that route, the timing doesn't matter: any time from an hour to three weeks after exposure would be equally effective. Which as it happens I wrote even before reading your "to summarize" statement: I couldn't have said it better. Syphilis never is a dangerous health risk until several weeks after acquisition. Finally, yes: syphilis is rarely transmitted by oral sex.---