HIV is an interesting virus in that left untreated it was passed on to offspring, and then they were likely to die before reproductive age.
However, it was not a perfect virus, even without advances in medicine, because it has been noted that the Delta 32 mutation might give people resistance to the virus, similar to the belief that this genetic mutation protected people from the plague. I guess another negative of the virus is it is not contagious through the air.
This article is facinating
http://www.pbs.org/wnet/secrets/previous_seasons/case_plague/interview.html
I worked with someone who was positive HIV and all of his frieds and boyfriend died years before I ever met him. He had been positive for 17 years last I saw him, never sick. His father lived to be 99, barely sick a day in his life, no major illnesses ever. I have to wonder if they had this mutation.