Naimi, your story is an incident on South Africa, a country which is close to 80% Christian and has the highest number of people with Aids in Africa. Catholics in South Africa make up 3.8% of the population, that's around 1.7 million people.
The estimate in 2009 was that 5.6 million people there were living with HIV and AIDS (
http://www.avert.org/aidssouthafrica.htm ). Now even if every single Catholic there had aids and was busy sha99ing everyone with a pulse at every opportunity, I'd accept that they were contributing to the spread of AIDS.
Of course they WOULD be disregarding the Catholic church's rules on sex, but you implied that people in Africa believe what they are told, and if they are told that it is wrong to have sex outside marriage - which is what the Catholic church would say - and believe it, and follow that teaching, they are not going to contribute to the spread of AIDS.
Now I do not deny that some Catholics disregard the church's teachings, nor do I deny that doing so may well help to the spread of AIDS. All I have said is that following the church's teachings does NOT contribute to the spread of AIDS, and so far nobody has been able to explain to me how they do.
In the only example that does work (Catholic woman married to non-Catholic man who is putting himself about) the spread is limited to one or two people, but is caused not by the Catholic but by the non-Catholic who is the one going out and getting infected in the first place.
And while it is nice to have a pop at the Catholic church, don't forget that the other Christian groups also say you shouldn't do sex outside of marriage. So if, in the case above, the man is a Christian, he is breaking the rules of his own church's teachings, which is hardly the fault of the Catholic church.