If my partner contracted HIV a week prior, how likely is it that I might had contracted the virus?
My gay sex partner (top) had unprotected sex a week prior to us having unprotected intercourse (I was not informed until after the act). How likely is it that he might have infected me a week later, if he was infected? Could he have produced enough viral count during that week to infect me? I started taking PEP on the 21 hour after potential exposure. What is the likelihood that once tested negative after the PEP treatment, that on the 2nd or 3rd months my test result could be positive? I worry mind would like to know.
Thank you so much for writing in. I know that after an experience like this people someone can feel betrayed and violated. You were very wise to consider your options and start PEP within 21 hours of the potential exposure. Not only was your partner capable of transmitting HIV during the first week he was infected, but he is actually MORE likely to transmit HIV during that first week.
After someone becomes infected with HIV, the virus begins to replicate very quickly and the amount of virus in the body and bodily fluids rises rapidly. Researchers estimate that the risk of transmitting HIV to another person from one act of unprotected sex is 26 times higher during the first three months after infection than during the months and years that follow (http://www.catie.ca/en/pif/fall-2011/recently-infected-individuals-priority-hiv-prevention).
I think the key here, however, is IF he was infected. I know it's scary to be in your position, but I wonder what his actual risk factors were? If he was a top with another guy then his risk of acquiring HIV were significantly reduced by about 90% (https://www.poz.com/article/HIV-risk-25382-5829). If his partner was HIV negative on PrEP then his ability to have detectable levels of HIV are nearly zero. If his partner was HIV positive and undetectable for six months or longer, his risk of acquiring HIV from that encounter was impossible (http://www.thebodypro.com/content/81184/gay-men-cannot-get-hiv-partners-virally-suppressed.html). Even if he was HIV positive and detectable with a high viral load, the chances of him transmitting HIV to you in that one encounter were only about 1.43%. Those are a lot of "IFS" working in your favor.
As far as getting accurate results to an HIV test after completing PEP, it depends on entirely on the kind of test you are given. Antibody tests generally have a window period of 3-12 weeks. But RNA tests, available in some parts of the world, have a window period of about 10-14 days. I would talk to your provider about what test you are being given so you have a better grasp on your status (http://www.sfaf.org/hiv-info/testing/hiv-test-window-periods.html).
You don't mention if there was an agreement or arrangement between you and your partner about how and when you have sex with other people. But you clearly state that you did not know he had unprotected sex with someone until after you had bottomed. This is exactly the circumstance under which many consider using PrEP for HIV prevention.
PrEP is a daily pill that prevents HIV while someone is HIV negative. In the U.S. gay men are 68% more likely to acquire HIV from a 'main' partner than a casual partner (https://www.npr.org/sections/health-shots/2013/10/18/236935146/to-prevent-hiv-infection-couples-try-testing-together). Especially when one enjoys receptive anal sex, PrEP is a means by which you can be in control of your sexual health regardless of your partner's HIV status or viral load.
Between the numerous variables and unlikely odds, combined with PEP started within 21 hours, it seems nearly impossible for you to have acquired HIV from this event. But I do hope it prompts you to consider your options for being in complete control of your sexual health. If there is a way to do so, I hope you and your partner can find a way to move through this with respect for one another, even if you choose not to continue your relationship.
To learn more about PrEP, please visit our resource page here at The Body: http://www.thebody.com/index/treat/tenofovir_prevention.html .
To discuss PrEP daily (and nightly) with people around the globe, please feel free to visit my Facebook "PrEP Facts" group: https://www.facebook.com/groups/PrEPFacts/.
Take very good care!