1.   If so, public health experts worry that the United States is vulnerable to a heterosexual epidemic much larger than what has been seen so far.

2.   In Africa and the rest of the developing world, AIDS is a heterosexual epidemic, and young African women bear the brunt of new infections.

3.   In this fashion, researchers believe, noncircumcising cultures may become especially vulnerable to a heterosexual HIV epidemic.

4.   While the epidemic in Europe and the United States remains concentrated among gay men, injection drug users and their partners, in Africa it is a heterosexual epidemic.