[Question #5710] In need of numerical risk assessment please

19 months ago
Good morning experts,

Please provide a numerical risk assessment(%) given my specific circumstances and how soon should I test for gonorrhoea, chlamydia,  syphilis and HIV. Of particular importance is the risk of HIV (especially given that I'm not in North America).   

I'm from North America but currently living in *Israel*. I met a man here of unknown status who said that he tested negative two months ago (he didn't specify what tests he's done), but then had an unprotected encounter with a woman of unknown status. He also expressed that he's not a "fan" of condoms, hence I'm assuming that having unprotected sex is more common for him than protected.  

On two occasions we've had oral sex (both giving and receiving), and about a week ago we had what has been initially protected intercourse, then condom was removed (not smart), and then there was a mix of oral sex and rubbing/making out. In the midst of all that he said that he "wants to feel" me and hence he penetrated for about 5-7 seconds and then was out thereafter as per my request. It's been a week since and I'm having out-of-control diarrhoea (which could be stress/anxiety-related, or not). 

How would you assess my overall (country-specific) and individual risks for the above-mentioned diseases?  Can I test for gonorrhoea/chlamydia already or should wait longer? For HIV I'm assuming it's about 6 weeks, although I'm not sure whether in Israel the test includes both antigen/antibody.  Lastly, I have no sores indicative of genital herpes, so I'm assuming that is okay.  My biggest concern is HIV risk. Please advise. Thank you. 
Edward W. Hook M.D.
Edward W. Hook M.D.
19 months ago
Welcome to our Forum. I'll do my best to help although data on the rates of HIV and other STIs in Israel are sparse.  HIV first.  What data there are from Israel suggest that HIV is relatively uncommon, being seen in less than 1/10th of 1% of the population.  In the instance you describe, you indicate that your partner was tested two months ago making it still less likely that he was infected and your unprotected vaginal penetration was brief, making transmission somewhat lower than the average risk of infection (1 infection per 12,000 sex acts) in the unlikely event that he was infected.  Your risk for HIV from giving or receiving unprotected oral sex is at least 10 times less likely than your risk from unprotected penetrative sex.  Putting all of this together, your risk is tiny, and not something to worry about.  You may want to test nonetheless.  If so, current combination HIV antigen/antibody tests provide reliable results 6 weeks after exposure and are over 99% reliable at 4 weeks (the last fraction of 1% take the final two weeks)

Your risk for chlamydia or gonorrhea from both the penetrative vaginal sex and oral sex is somewhat higher than your risk for HIV (again, there are few statistics to call upon) but the good news is that now, five days after your encounter, you can be tested for gonorrhea and chlamydia and your test results will be entirely reliable.  Syphilis is very rare and primarily an infection which occurs amongst men who have sex with other men so while you may choose to test for it at about the time you test for HIV, your risk for infection is quite small.

Bottom line, provision of specific numerical estimates is not possible however, given the nature of your exposures (oral sex being far lower risk than penetrative vaginal sex) and the brevity of your unprotected vaginal sex, as long as he truly did get tested two months ago if very, very low (less than 1% for all STIs, including HIV).  Testing for gonorrhea and chlamydia will be reliable at this time, testing for HIV and syphilis which are still less likely needs to wait until 4-6 weeks after your exposure.  

As far as your current diarrhea is concerned, this is unlikely to be due to any STI.  As you suggest, anxiety could be a contributor.  EWH
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19 months ago
Thank you for your reply, Dr. Hook! 

Just to clarify: Given my exposure, my risk is 1/12,000 acts or even lower than that? Because that still seems to be a rather high risk. I was hoping the likelihood would 1/hundreds of thousands per this act. Maybe I have my math wrong, but now I'm pretty concerned (and the diarrhoea isn't helping). 
Speaking of which,  based on your practice/experience,  have you seen stand-alone symptoms such as diarrhoea, or do they tend to occur in clusters and hence the term "acute retroviral Syndrome"? I still have about 3-4 weeks until testing and anxiety--justifiably or not--is really starting to kick in, which is why I'm trying to approximate via numbers how sizeable this exposure was (although, of course, there can never be certainty). Have you had in your practice individuals who acquired HIV from a single exposure? Please weigh in and apologies for all this anxiety. 
19 months ago
Just to add (and I realize it's my last reply): I was able to find an epidemiological report wherein it's indicated that that in 2017-2018 there were about 9,000 people living with HIV/AIDS in Israel, while the population total is about 9 million. I believe that makes 1/1000 carrier/diagnosed with AIDS.  The risk of an unprotected vaginal receptive act is 1/1250. If I multiply the risks of 1/1000  times 1/1250, that makes the cumulative, per act risk 0.0000008.  Please advise if this arithmetic makes sense or if I have made an error. Thank you again. 
Edward W. Hook M.D.
Edward W. Hook M.D.
19 months ago
Several thoughts.  First I was about to reply that I think your math was overly conservative but you beat me to that assessment with your follow-up e-mail - I agree with your 2nd calculation.  Secondly is the issue of "risk" people think of these things differently.  Did you know that your risk of being struck by lightening is about 1 in 10,000?   While no one should take unnecessary risks, the single exposure you mention while perhaps troublesome, is numerically just not that great (in my view), not that I'm encouraging you to have unprotected sex with partners of unknown status.  

Finally, diarrhea alone in no way suggests the ARS.  A high fever, sore throat and sever muscle/joint aches are prominent in the ARS.  Further, as an FYI and to try to help you address your anxiety, IF your diarrhea were a manifestation of the ARS (I am confident it is not), a 4th generation, combination HIV antigen/antibody test would be positive after a day or two of symptoms.  Thus, if it would help your anxiety, while the results would not be entirely conclusive, if you have a negative test at this time, it will conclusively show that that your diarrhea is NOT due to the ARS.

I hope these further comments are helpful.  EWH
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