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Avatar universal

HIV Transmission from Unprotected Oral

Dear Drs. HHH and Hook,

Thanks in advance for answering my questions.

I am an uncircumsized heterosexual male. I've had 6 single exposure unprotected oral sex with white women (can't be sure about their HIV status) in the past 2 years.  The latest unprotected cunnilingus was just over 7 weeks ago and the latest unprotected fellatio (I received fellatio) was about 6 months ago.  No symptoms (no fever, no sores, I believe no rashes, no painful urination).  I went to the clinic for testing for STDs and HIV this past Tuesday and waiting to hear my results.  I am very very anxious (lack of sleep and appetite) and most concerned with HIV.

Questions in my head that really got me worried:

1. I've read these forums carefully and saw estimates for unprotected oral sex being somewhere around 1/10,000 to 1/20,000, how did the CDC come up with these estimates? Personal reports?

2. Some people in this forum have said "no risk" or "zero risk" and have cited the Spanish serodiscordant study with zero HIV transmission from unprotected oral sex and also some UCSF studies on gay men (although these studies were not consistent mostly because of unreliable reports).  Are these studies really applicable in my situation?  The Spanish studies are with HIV positive people under treatment and with low viral loads (viral loads are highest in people who would not know their HIV status especially if they had just been infected).

3. The few documented cases of HIV transmission from oral sex (although not verified), where they all transmission from penile to oral partner; in other words, the person performing fellatio was infected with HIV?  I believe Dr. Cummings mentioned there has been no documented cases of HIV transmission from having one's penis sucked and only a handful out of 85 million cases worldwide from performing cunnilingus and these were mostly in menstruating women.

4. Should I expect a negative HIV result given 6 exposures of unprotected oral sex?

Thank you so much.
6 Responses
239123 tn?1267647614
MEDICAL PROFESSIONAL
Welcome to the HIV forum.  Your questions are good ones; they have been discussed many times, but the information bears repeating.  I'm going to take the time for a comprehensive, blog-like reply which can be used later for future questions about oral sex and HIV transmission.

The bottom line is that you were not at any measurable risk of HIV, not only because oral sex carries little or no transmission risk but also because it is statistically very unlikely your partner has HIV.  To the specific questions:  

1) CDC analyzed reported new HIV infections, the sexual exposures they described, and data on the prevalence of infection in the population -- i.e. the odds a particular partner had HIV.  The results are not very precise, but are certainly valid as ballpark estimates.

2) I agree the data from Spain are biased because of treatment and low viral loads.  But the CDC data cited above were mostly collected before antiretroviral therapy was available.  The transmission risk undoubtedly is higher if the infected person has a high viral load.  But doubling or even a tenfold increased risk doesn't mean very much when the baseline chance of transmission is very low to start with.

3) The CDC data suggest a transmission risk for fellatio of 1 in 20,000 if the oral partner is infected and 1 in 10,000 for the oral partner if the penile partner has HIV.  Whether a case is "documented" or not depends on the definition.  But I agree with Dr. Cummings -- to my knowledge, there has never been an unequivocally documented oral to penile transmission.  I'm not aware of any documented cases of transmission by cunnilingus -- Sean may know of data that I missed.  It is a semantic issue whether a particular advisor or expert uses a term like "zero risk" or qualifies it with "virtually no risk", "exceedingly low risk", or "no measurable risk".  I have used all those terms and for the most part don't mean anything different by them.  For example, the 1 in 20,000 estimate is equivalent to receiving oral sex by infected partners once a day for 55 years and maybe never catching HIV.  In my book, that translates to "zero risk" (or "virtually zero risk") for any single exposure.

4) For sure you can expect your test to be negative.  Any particular "white woman" in the US has around a 1 in 1,000 chance of having HIV.  After 6 exposures the chance you caught HIV by receiving oral sex can be calculated at 0.001 x 0.00005 x 6 = 0.0000003.  That's 3 chances in 10 million, or 1 chance in 3 million.  Now let's put that figure into a broad context.  According to the National Safety Council, 1 of every 1,765 residents of the US dies accidentally (motor vehicles, falls, drownings, etc, etc) every year.  In other words, the chance you have HIV is almost 2,000 times lower than the odds you'll be dead of an accident within 12 months.

5) Your follow-up question below goes to the window period, i.e. how long after exposure to be sure a negative result is valid.  With standard HIV antibody tests, it's rarely if ever longer than 6 weeks; with the duo test (antibody plus p24 antigen) it's 4 weeks.  Here is a thread that explains why, despite these figures, many agencies still recommend testing at 3 months:  http://www.medhelp.org/posts/HIV-Prevention/-A-Question-on-Testing/show/1347755

Bottom line:  Stop worrying about HIV on account of this relationship.  There is no realistic chance you caught HIV and your test result will be negative.  But don't forget your seat belt!

Regards--  HHH, MD
Avatar universal
Sorry, I forgot to also ask:

5. How conclusive are the results of HIV 48 days post last unprotected oral exposure?  Should I test again at 3 months post exposure?  I'm in the United States (not sure which test they used, but they withdrew blood).
239123 tn?1267647614
MEDICAL PROFESSIONAL
See above.
Avatar universal
Dear Dr. Handsfield,

Thanks for answering all my questions.  After calling the doctor's office I was notified "good news all the way around," which I take it to be that I have no STDs and I am HIV negative.  

1) I read the thread you linked above, but still unsure. Would you say that testing HIV negative with ELISA (Ab test) 7 weeks after unprotected cunnilingus is 90-95% reliable?  In other words, there is only a 5-10% chance that the time window is beyond 7 weeks.

Also, I would like to educate myself on HIV prevention further.

2) Could you please post on here the citation or link for the scientific article that discusses the findings of the Spanish study?  I would like to look through the data and see to what extent they controlled for viral loads. Any other citations you feel are high quality and pertinent are appreciated as well.

3) General thought: I could be wrong, but my assumption is that most new HIV transmission cases occur between individuals who do not know that they are HIV positive. Ideally, there is a study under way that looks at transmission rates as a function of time post new infection. Such a study would require testing high risk individuals and their partners regularly to catch a new infection and subsequent transmission.

Thanks again!
239123 tn?1267647614
MEDICAL PROFESSIONAL
1) 99-100%.  There is less than a 1% chance the window will be beyond 7 weeks.

2) I think this is the correct citation:  Vargehese B et al. Sex Transm Dis 2002;29:38-43.

3) I agree.
239123 tn?1267647614
MEDICAL PROFESSIONAL
Correction:  The citation above is only one of several whose results were compiled by CDC into the following report; see Table 1.

CDC. Morbity and Mortality Weekly Report (MMWR) 2005;54 (No. RR-2); available at http://www.cdc.gov./mmwr/PDF/rr/rr5402.pdf
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