[Question #1762] Are these my odds? HIV...

79 months ago

Hello Doctors,

I am a lifelong healthy male who, last summer, had unprotected vaginal and oral sex with a female who claims to be HIV negative. Somewhere around 3/4 weeks after the encounter I began to feel terrible. Light fever, lot's of fatigue, total loss of appetite, change in stool patterns and coloration, night sweats, among other things. It's been about 7 months since the incident and I'm happy to say that almost all of my symptoms have resolved. I still have some swollen taste buds and a bit of a cotton mouth.

During this time I tested for all STD's, the results always being negative. I specifically tested for HIV 8 times. 3 times were with an oraquick (which I believe were inside the test window period), 2 times with an HIV RNA (about 1 and 1.5 months after exposure) and 3 times with a 4th generation duo test (earliest was 2.5 months after exposure, latest was about 5 months after exposure).

My odds of meeting a female in the U.S. who has HIV, 1/500. My odds of contracting HIV from unprotected vaginal single exposure, 1/1000. Odds of 5 highly specific, highly sensitive, highly accurate HIV tests giving a false negative within the test time frames 1/495. So my odds of having HIV are 1/247,500,000.

1). Would you agree that these figures are in the ballpark?

2). Are the odds good enough to call myself conclusively HIV negative requiring no further testing?


H. Hunter Handsfield, MD
79 months ago
Welcome to the forum. Thanks for your question. It seems you probably have reviewed other questions like yours; we frequently offer statistical estimates of HIV infection much like your own. Thank you.

You've done a good job, except your baseline estimates all are too high, and your actual risk is at least a thousand times lower than you calculated. The chance any particular sexually acrtive woman in the US has HIV, assuming she isn't a commercial sex worker, probably is less than 1 in 1,000, not 500, and probably a whole lot lower (mabye in in 10K?) in those who say they have been tested with negative results. (People rarely lie about HIV status when asked directly.)  Second, CDC's calculation of risk published several years ago came up with 1 in 2,000 for vaginal sex, female to male, if the woman is infected. (They estimated 1 in 1,000 for male to female transmission.) Finally, most experts disblieve the official statistics on test performance. The chance of a false negative HIV test result, beyond the window period, probably is a lot less than 1 in 495. (Actually, I'm not aware of any published data on this. What is the source of that figure?) Finally, the combination of two different tests -- antibody (Oraquick) and RNA testing -- is absolutely conclusvie. So much so that with the combination of antibody plus RNA testing of all blood donations, transfusion related HIV has been eliminated in the US.

Based on this single exposure, I wouldn't have recommended HIV testing at all. For those nevertheless seeking testing for reassurance, a single duo test 4 weeks or more after the last exposure would have been conclusive. For sure your result was conclusive once you had the first antibody test plus the first negative RNA test. 

Those comments pretty much answer your questions. But to be explicit:

1) To the extent that 1 in 247 million is zero for practical purposes, your calculations are "in the ballpark". However, if I were doing a numerical calculation, I would say truly zero chance; or maybe 1 in 247 billion instead of a million.

2) You have been seriously overtested already and for sure should not have any more tests. 

I hope these comments have been helpful and reassuring. Let me know if anything isn't clear.


79 months ago
Hi Dr. Handsfield,

I have read many of your posts mostly on Medhelp. Im glad to hear my own personal assessment is even more conservative than yours.

To your question regarding the 1/495, I do not have a source. I assumed the worst case scnenario for a false negative for the performance of the 3 Duo tests and 2 RNA tests at 1/100. Therefore 5x99=495. Also glad to hear that in your opinion the test performance is even better.

It's frustrating to hear uneducated physicians wanting to continue to test to 6 months or even 1 year after exposure. I'm done testing for this exposure, I can tell you that much.

I think it's far more likely what I had was mono via EBV infection. I never tested positive for the EBV IGM antibody (probably tested too late to see it), but I did test positive for the Early Antigen Ab IGG, which then later disappeared. Consistent with the serologic profile of an acute infection.

Thanks for the discussion. All the best.
H. Hunter Handsfield, MD
79 months ago
Thanks for the follow-up comments.

There is a basic mathematical error in your reasoning above. If 5 tests each have 99% reliability, you don't multiply x5 to get to 495. You take the opposite proportion, i.e. 1% chance the test misses the infeciton, and multply 0.01 x 0.01 x 0.01 x 0.01 x 0.01 = 0.0000000001. That's not 1/495 odds that all 5 tests were wrong, but 1 in 10 billion. (So now I have to modify my own estimate above. My guesstimate of 1 chance in 247 billion you have HIV is far too high. Maybe 100 or 1000 times lower still.)

I suppose it is possible you had mono due to EBV, but it's rare beyond age 20 (although I don't know your age). Most likely the illness had nothing to do with the sexual exposure 3-4 weeks later. In any case, you'll never know for sure and at this point I don't see that it matters much.

Anyway, for sure no HIV, so that issue is a done deal.

79 months ago

Ah yes Doctor, you are correct. That was a silly math error on my part. In any case, it appears the odds are miniscule and asymptotically approach 0. 

I am 30 years old and thereby fully agree with you that I should have had Mono/EBV a long time ago given the statistics. I've had somewhere around 10 partners in my life, so it would make sense that I have it by now. For whatever reason, the testing indicates differently. I also can't remember ever having been this fatigued/ill before, so maybe it was my first encounter with it. Maybe it was something else all together... who knows.

I can only hope my lingering issues resolve over time. Thanks again for your insights and take care. 

H. Hunter Handsfield, MD
79 months ago
Number of sex partners isn't documented to correlate well with acute EBV infection. For sure a modest minority of EBV/mono is acquired sexually, as studied mostly in college students. However, most infections are acquired in childhood through saliva exposure, before onset of sexual activity.

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!