Although there is no evidence to suggest a direct causal pathway, some intravaginal practices used by women in sub-Saharan Africa (such as washing the vagina with soap) may increase the acquisition of HIV infection and so should be avoided. Encouraging women to use less harmful intravaginal practices (for example, washing with water alone) should therefore be included in female-initiated HIV prevention research strategies in sub-Saharan Africa.

These are the key findings from a study by Nicola Low, from the University of Bern, Bern, Switzerland, and colleagues and published in this week's PLoS Medicine.

The authors pooled individual participant data from 13 prospective cohort studies in sub-Saharan Africa involving nearly 15,000 women, 791 of whom acquired HIV, and found that HIV infection within two years of enrolment in the studies was associated with self-reported intravaginal practices. After controlling for age, marital status, and the number of recent sex partners, women who used cloth or paper to clean their vagina were nearly one and half times more likely to have acquired HIV infection as women who did not use this practice. Furthermore, the insertion of products to dry or tighten the vagina and intravaginal cleaning with soap also increased women's chances of acquiring HIV. Intravaginal cleaning with soap was associated with the development of bacterial vaginosis, and disrupted vaginal flora -- two conditions associated with an increased risk of HIV acquisition.

These findings add to the results of a recent systematic review, published in PLoS ONE, which suggested that a pathway linking intravaginal cleaning practices with vaginal infections that increase susceptibility to HIV infection is plausible, but conclusive evidence is lacking.

The authors of the PLoS Medicine study say: "New female-initiated interventions also need to be developed despite the challenges involved in measuring the impact on preventing HIV acquisition. Behavioural interventions that have been successful in helping young US women to stop vaginal douching might be adapted for women in sub-Saharan Africa to encourage less harmful practices."

Funding was received from the Office of AIDS Research, US National Institutes of Health.