The level of HIV-1 in the blood of an HIV-infected partner is the single most important factor influencing risk of sexual transmission to an uninfected partner, according to a multinational study of heterosexual couples in sub-Saharan Africa.The study, published in the Journal of Infectious Diseases, calculated the risk of HIV-1 transmission per act of sexual intercourse and found the average rate of infection to be about 1 per 900 coital acts…. click here for more..