Through 2007, about 175,000 AIDS cases in the US were heterosexually transmitted. That’s about 20% of the total. Internationally, the percentage of cases with heterosexual transmission is much higher. I’m not sure “rarely” is quite the right word.
175,000 cases compared to the total number of heterosexuals is rarely. There are far, far fewer homosexuals and far, far higher number of cases with them.
I challenge your sources, asserting “hetro transmission”.
Did they rule out I.V. drug use?