Thank you for all you do. I've used this service in the past and your advice has been helpful. If only I could refrain from making the same mistakes time and again, but that's a different story.  I'm hoping for a numerical risk assessment for the following specific situation: I have recently met a 39-year-old man, he's straight, has been in a relationship for about five years, recently it ended, and thereafter he's had a casual relationship where he engaged in a combination of protected and unprotected sex.  He doesn't know his status at present, but did advise that he undergoes testing annually. That's as much history as I was given by him.  Two days ago we had 4 instances of protected and unprotected vaginal sex in the course of one night. I insisited on wearing a condom at first, but then my judgment lost its solid ground (unfortunately), so to speak, and we had unprotected vaginal intercourse. Two days after I'm asymptomatic, but that makes sense given how soon it is after the event. In any case, I understand that testing is superior to symptoms. Can you please provide a specific risk assessment given this event? I know the risk is 1/1000 or so for a receptive partner per one incident. Given the fact that it was 4 separate instances during one night, does the risk increase to 4/1000  which is then multiplied by the numerical likelihood of the man having untreated HIV? How does math/probability work in this particular scenario? What is the end probability? Also, for chlamydia and gonnorhhea, do I need to wait a week to test or shorter time span is sufficient for conclusive results via urine? I do have some (vaginal) spotting happening right now, but I don't know if it's a symptom of any kind or just a prelude to my menstrual cycle that is about to start.  Your advice would be much appreciated. Thank you.  

The bottom line is that based on all you say about these particular exposures, the chance you have acquired HIV is extremely low. Beyond that, a detailed numerical estimate probably isn't very helpful, in my opinion. Whether the true risk calculates to say 1 in a million versus 1 in 10 million probably doesn't make much difference. In general, my advice about HIV and STD testing is that they usally are not needed or recommended after any single eposure, unless there is reason to believe the risk is unusually high -- such as unprotected sex with a known infected person, sympoms highly typical of a new infection (as opposed to vague and nonspecific symptoms), and so on. A smarter approach for sexually active presons with occasional new partnerships is to plan on periodic testing, e.g. annually or maybe every 6 months, depending on the frequency of new partnerships, their sexual and social histories, and so on.

To your specific questions:  I would judge there is almost no chance your partner had HIV, making your HIV risk virutally zero -- regardless of how many intercourse events there were. But if you'd like to assume there is 1 chance in a thousand your partner had chronic, untreated HIV, then a reasonable calculation of your risk would be 0.001 x 0.001 x 4 = 0.000004, or 1 chance in 250,000. Low enough to not be tested, in my opinion.

The risk of gonorrhea and chlamydia is almost always higher than for HIV, because both infections are far more common and transmitted more effeciently. Still, not many men his age are likely to have either infection -- both are quite rare beyond age 30 (chlamydia) to 35 (gonorrhea). That said, vaginal spotting is a common symptom of either of these STDs, so it would make sense for you to be tested. The standard tests are accurate and valid within 4-5 days of the last exposure.

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

HHH, MD

Threads are closed after two follow-up questions and replies, or 4 weeks, whichever comes first. If you have STD testing, gonorrhea and chlamydia results will be available and valid well within that time. And since the chance you caught HIV is virtually zero, you can count on that being negative as well -- in which case, there shouldn't be a need to discuss it with us. If you have an AgAb (4th generation) HIV blood test 6 weeks or more after the last exposure, there is no chance we would do anything more than assure you that the result is valid. (FYI, contrary to urban myth, there are no medical conditions or drugs that have any effect on the reliability or timing of any HIV blood test.)

I was tested for chlamydia, gonnorhea and trichomonos. I was found positive for chlamydia (even though it's rare in men over 35), which will be addressed via an antibiotic with my GP. Gonnorhea and trichomonas tests were negative.  Today is day 11 after uprotected vaginal intercourse (4 instances), so I am thinking of doing a preliminary test for HIV. You have indicated in the past that around 90% of new infections show positive result at this time. I am hoping that won't be the case for me. I have been asymptomatic thus far, but you have mentioned in the past that often times newly infected are asymptomatic and many don't get ARS.  Do you think that the fact that I'm positive for chlamydia sizably increases the risk for HIV? Or do you still maintain that it's "virtually zero" as you have stated in your previous reply (given my particular exposure)? Please advise. I'm very, very worried at this stage and I wasn't that way before. Thank you. 

The chance you have HIV remains exceedingly low. If your partner isn't an injection drug user, bisexual, or otherwise at especially high risk, the chance he has HIV is under 1 chance in several thousand -- regardless of the chlamydia. But of course you should follow through on plans for teting:  anybody with any newly acquired STD needs HIV testing as a matter of routine. However, I really don't think an RNA test (the only test that would detect almost 90% of infections at 10-11 days) is worth the high cost. If you were my patient (or someone close to me, say my daughter) I would advise just wating until the 6 week mark and have an AgAb ("duo", "4th generation") blood test. You're going to need to do that anyway, even after you get the negative RNA result; and you also need a syphilis blood test at 6 weeks.

Alternatively, discuss all this with your partner. You need to tell him about your mutual chlamydial infection anyway. When he learns of your chlamydia, you may find he is freaked out about other STDs, including HIV, and would agree to be tested. Iin addition to chlamydia and HIV testing, he also should be tested for gonorrhea and syphilis.) If both of you have negative AgAb tests at this time, you'll both know for sure neither was at risk.

Perhaps you'll also be reassured to know that in the 16 years of this and my preceding forum, with thousands of questions from people worried about HIV, not one has turned out to be infected. You won't be the first! If and when that happens, almost certainly  it will be from a triditional, truly high risk exposure (like anal sex between men, or unprotected sex with a known infected partner -- or at least one at genuine risk for HIV). So go ahead with whichever HIV test(s) you wish, but stay mellow in the meantime. There is very little chance of a positive result. 

That completes the two follow-up exchanges included with each question and so ends this thread. I hope it's been useful. Best wishes and stay safe.