If they're Catholic married couples living by the law of the Church, they wouldn't be sleeping around and picking up AIDS in the first place.
While it may sound cruel, sometimes the natural consequences of disobedience to God's law can be among the things that make people heed it. Interestingly, I read once that one of the reasons for the success of the Jews was that they tended to live fairly long lives, enabling them to have many children, as a result of the fact that they followed Jewish law and did not eat pork. Trichinosis was endemic in pigs in that area (because pigs were fed garbage and roamed and rooted and picked up larvae) and evidently non-Jewish neighbors who did eat pigs died in large numbers from the disease. Obviously, this is not the case anymore and it has now become more of a sign of identity; but at one time, it had a practical impact.
In the 18th and 19th century England, there was a phrase, the "Marriage Hearse," that described the fact that many men slept around and got syphilis, which was incurable at that time, and passed it on to the decent young women they married - who of course then died of syphilis, but without being in any way responsible for it.
Life is better and probably longer if you live it according to the dictates of the Church and God's law. And the Church has got to hold firm and tell people this; it may be better in many intangible ways, but it is also better in practical ways.
Did you know, for example, that black Catholics in the US have a higher average annual income than white Catholics (even though blacks as a whole have a lower one)? In other words, marrying, staying married, abstaining from violence and crime, and in general obeying the 10 Commandments and the commandments of the Church are a good basis for a successful life, as well as for avoiding death from STD's, and all this without even going into the consideration of eternity...
The human body and soul was invented, designed and built by GOD. The 10 commandments are the brief version of the Owner's Manual ... RTFM, folks! If you use the device at variance with the manufacturer's instructions, the results are likely to be less than optimal.