So, whether or not you have HIV, STIs increase the risks. Because you can have an STI without knowing, a check-up at a sexual health clinic will let you know for sure. Some men have regular check-ups for STIs so that they can have any infection treated quickly. Men who aren't infected have no HIV and so cannot have a viral load. The higher someone's viral load, the higher the chances of HIV being passed on during unprotected sex.
Tests can give an idea of what the level is.
Having an infection or being run-down can make it easier for HIV to be passed on. Whatever a man's viral load, there is still a risk of infection if he and a man without HIV fuck without a condom. Some people take viral load into account when thinking about what kinds of sex to have, like whether to fuck and whether or not to use condoms. If you don't have HIV you can't pass it on For HIV to be passed on during sex, one of you has to have it already. If neither of you have HIV you can't get it by fucking together, even without a condom.