. . which is where Aids is really ripping things up these days. It spreads easily through heterosexual contact when other diseases have already weakened the system.
In the U.S. there's still typically a male homosexual or bisexual vector nearby, though hetrosexual transmission is certainly significant, again particularly in the "less advantaged" communities where other diseases assist.
The original fast spread of Aids in the U.S. was by the male homosexual community who's practices make them particularly vulnerable, and particularly by a certain Canadian airline host who did it deliberately and gloated "By the way, I have 'the disease', so you probably have it now too". He should have been strangled right off.