HIV transmission is dependent on the route of acquisition, the infecting viral load and the presence of inflammation and activated immune system cells below mucosal surfaces.8 Addressing these factors lowers HIV transmissibility. Unprotected, especially receptive, anal sex remains a high-risk behaviour for HIV transmission with a transmission risk about 18 times higher than for penile-vaginal sex, and is a major driver of high HIV rates among MSM.9 IDUs who inject themselves with HIV-contaminated needles provide a direct access point for HIV, and established infection can therefore occur with relatively lower viral loads. CSWs are likely to transmit HIV if they become infected themselves because of the greater number of sex partners that they encounter. All these population groups benefit from targeted HIV programmes.
