Strategic Positioning: Top or Bottom?
Some HIV-negative men think it’s safe for them to have anal sex without effective risk prevention tools, even with a partner who is HIV positive and isn’t undetectable, as long as they are the one topping (the penetrative partner). Similarly, many HIV-positive men who aren’t undetectable think they can have unprotected anal sex, as long as they are the receptive partner or bottom. But whatever position you assume (and many assume both), anal sex without HIV/STI preventative tools is a high risk for picking up or passing on HIV.
Being a top is NOT a reliable technique to avoid getting HIV during anal sex without HIV/STI preventative tools. It reduces your risk of picking up HIV, but still remains risky because HIV can enter the body through the tip of the penis and possibly the porous cells of the foreskin.
Undetectable Viral Load
The BC Centre for Excellence in HIV/AIDS and other HIV/AIDS research institutions have found that the risk of HIV transmission for sero-different couples (one is positive, the other is negative) is nonexistent if the HIV-positive partner is on treatment, has an undetectable viral load and is free of STIs.