We all know the safer sex rules: „when you fuck someone or you get fucked always use a condom“, and „when you go down on someone don’t let him come in your mouth“. What's new is: the HIV treatment of a positive partner can prevent transmission too - just as reliably as condoms. If the viral load is permanently undetectable, an infection is not possible. While a condom can be used without any Q and A, when it comes to “safe sex 3.0,” it‘s a matter of talking and trust. That's why we recommend the so-called viral load method (treatment as prevention) mainly when having sex with people you trust. In the end it depends on how far you trust your (sex) partner.
HIV drugs stop the virus from multiplying in the body - virtually no virus can be detected in the blood, cum, and anal mucosa under a successful HIV regime. An infection becomes impossible.
Taking the medication regularly is vital: if the treatment is interrupted even just for a few days, the viral load of the blood usually increases again quickly - and a little later the same happens in the bodily fluids.
Do other sexually transmitted infections increase the risk when using "treatment as prevention"? Probably only marginally. But the scientific community is still divided on this issue. There is for instance the question of whether or not the risk could increase too much with an acute syphilis infection, as this can increase the number of HI viruses in the body.