Roughly a quarter-century after gay men rose up to demand better access to H.I.V. medicines, a new breed of AIDS advocate is growing up on college campuses. Unlike the first generation of patient-activists, this latest crop is composed of budding public health scholars. They are mostly heterosexual. Rare is the one who has lost friends or family members to the disease. Rather, studying under some of the world's most prominent health intellectuals, they have witnessed the epidemic's toll during summers or semesters abroad, in AIDS-ravaged nations like Rwanda, Tanzania and Uganda.