This is a reasonable question. Technically, you are correct:  if both partners test negative, it is conceivable that one of them has a recently acquired infection and the HIV blood test hasn't had time to turn positive. This is a potentially very high risk situation:  the viral load (amount of virus in blood and genital fluids) and potential for transmission may be very high. However, the actual risk depends largely on their sexual lifestyles and ongoing risk for HIV. For the average person who may select a new partner at low or average risk of HIV, almost certainly their mutual negative test results indicate no risk. However, if either partner recently has had frequent unprotected sex in a geogrpahic area where HIV is common, I would advise testing at least 4-6 weeks after the last unprotected sex. If you continue to reside in a high risk community (as indicated in your two forum questions over a year ago), and if your potential partner might be quite sexually active, it would make sense to delay sex accordingly. Until your partner has been tested 4-6 weeks after a previous partner, you either should delay sex entirely or be especially careful about safe sex practices, e.g. using condoms or avoiding vaginal or anal penetration.

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

HHH, MD

Thank you for your reply. However I am confused because your colleague Dr. Hook seems to have a contrary opinion. Below is his reply for the same question last year about unprotected sex in the window period, please also look at the question I asked at the time. (I had also asked about HIV from the barbershop which is why he made reference to barbershops in the reply)

...... If a person is in the window between acquisition of HIV infection and having a positive combination HIV antigen/antibody (fourth generation) test become positive, the risk of HIV trans mission is virtually zero. There must be virus present for transmission to occur. Typically following acquisition of infection virus levels quickly become very high and are easily detected by VP 24 antigen test.I hope these replies are helpful. I would have no concerns about acquisition of HIV either from receiving a haircut at the barber shop or if I had had direct contact with a person who had a -4th generation HIV test. EWH.......

You can see his reply in my previous post from last year. Please clarify as I am confused.

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.