Other factors that may affect transmission risk

The chances of infection may be lessened if ejaculation does not take place. The European Study Group on Heterosexual Transmission of HIV noted that after 20 months, none of the couples who had consistently practised withdrawal experienced the seroconversion of the HIV-negative partner.¹(However, see the section on anal intercourse, discussing studies have found that intercourse without ejaculation did not significantly reduce the risk.)

Rougher sex and/or vaginal dryness may lead to vaginal or penile abrasions, which may increase the chances of infection. A number of studies have also suggested a possibly increased risk of HIV infection when the hymen is broken on the first occasion of sexual intercourse.

Reduction of vaginal lubrication becomes more common with age, and some researchers say that this is one reason why some studies show higher rates of HIV infection amongst post-menopausal women. Younger women in early puberty may also produce less vaginal and cervical secretions, perhaps increasing their vulnerability to HIV infection and contributing to the disproportionate prevalence of HIV amongst adolescent women. Hysterectomy in older women may also increase the risk of HIV infection in older women.²

Deficiency in blood levels of the mineral selenium has been associated with increased rates of vaginal HIV shedding in a study conducted among women in Kenya. HIV-positive women with selenium deficiency were almost three times more likely to have evidence of HIV DNA in their vaginal fluids when sampled (once only).³ It is not clear whether selenium deficiency might affect plasma viral load, which could in turn affect vaginal HIV levels.