As I understand it, you can only get infected by HIV if blood or semen from an infected person enters your bloodstream. Aside from sharing needles with an infected person (which seems to be by far the riskiest activity) this can happen when a small wound present during, or caused by anal sex allows semen containing HIV to enter the bloodstream, when a small wound preent during or caused by vaginal sex allows semen into the bloodstream, or when a wound, a sore, or damaged gums allows semen into the bloodstraem during oral sex. If there is a wound or sore on the penis, there is also the possibility of a man acquiring HIV from either a woman or a man during either anal or vaginal sex.

As I understand it, there is little or no risk of getting HIV though swallowing the semen or urine of an infected person, as long as no semen or urine enters the bloodstream directly through a cut or sore.

It would follow from this that the risk to a man or woman who is the passive partner in anal sex will be greater than during vaginal sex as the risk of a wound occurring is greater. However, I know of no study that indicates that black, or specifically black men of African origin, participate in anal sex more than any other group. Moreover, few men of any racial origin worry too much about contraception with casual sexual partners. So I suspect the high incidence of HIV among African women and men arises from promiscuous vaginal intercourse rather than anything else.

On the issue of oral sex, there is conflicting advice on internet sites whether or not there is an increased risk if someone comes in your mouth, and whether you should avoid brushing your teeth before having oral sex.

Finally, I would offer anyone still reading this one piece of advice. Don't rely on any medical information or advice you read on a message board such as this one, not even if it comes from me. Read advice from as many different and (so far as you can tell) reliable sources as you can, then form your own judgement.