When I was growing up, the lesson drilled into our heads was that anyone can get AIDS.
Real life experience hasn't borne that out. The only people I knew who got AIDS were gay males. I don't know one single straight person, no matter how promiscuous, who got AIDS.
If you look at AIDS cases, upwards of 90% are men who have sex with other men, prostitutes and intravenous drug users. For the average straight person, AIDS is well down on the list of things to worry about.
Basically it boils down to the simple conclusion that people are nowhere as promiscous as latter day liberal wisdom would have us believe. Just because they are rutting with anything - male, female, animal or mineral - that moves does not mean that we all are.