de Melo MG, Sprinz E, Gorbach PM, et al. - Researchers examined 200 HIV-1 heterosexual serodifferent couples in a stable relationship (> 3 months) for the risk of sexual HIV-1 transmission and other sexually transmitted infections (STIs) while the index partner was on antiretroviral treatment. Seventy percent of the index partners were female. They noted five seroconversions; HIV infection incidence was 2.5%. HIV transmitters vs non-transmitters showed higher mean plasma virus load results. Couples who seroconverted had a significantly higher presence of STIs. In their setting, the main factor associated with non-transmissibility of HIV was undetectable viremia.