STDs are a myth.

[LordSappington]

If your parents had an STD, say, AIDS, did the deed and you were conceived, wouldn't you be born with AIDS yorself? I dunno if it works like that for AIDS (I imagine it would, I mean, why not? THe AIDS cells are being transferred to the fetus through the cord) then you could have a straight person with AIDS, and then the straight guys can get it from him/her/whatever.
tl;dr YOU DON'T HAVE TO BE GAY
Also, I agree with MattJack; if you had AIDS, you wouldn't want to bring it up a lot. AIDS is pretty embarrassing, I'd imagine, to talk about, let alone go around spreading the news of your entry into the Horde.