There are several factors that increase or decrease the risk of sexual transmission of HIV. For example, individuals who are newly infected with HIV or who have AIDS are more infectious because they have higher levels of virus in their blood and genital secretions. Antiretroviral therapy lowers the amount of virus in an infected individual and therefore reduces the risk of transmission. STDs, both ulcerative and nonulcerative, increase both infectiousness and susceptibility to HIV approximately 2–5 times. Uncircumcised men appear to be at increased risk of transmitting and acquiring HIV. When a woman is menstruating, pregnant or has cervical ectopy, she may have an increased risk of HIV transmission. Barrier contraceptive methods, including the male and female condom, provide the greatest protection against both transmission and acquisition of HIV. The role of hormonal contraceptive methods in HIV transmission is inconclusive, although some data suggest that they may increase genital tract HIV shedding. Although spermicides (most of which use nonoxynol-9 as the spermicidal agent) have activity against HIV in the laboratory, a recent clinical trial conducted by UNAIDS in Africa and Thailand in sex workers who averaged over 3 partners daily found significantly increased rates of HIV seroconversion in nonoxynol-9 users as compared to placebo. Finally, the IUD was associated with increased susceptibility to HIV transmission in an Italian cross-sectional study, but not in prospective studies.