(HealthDay News) – Bacterial vaginosis is associated with a three-fold higher risk of HIV-1 transmission from infected women to their uninfected male partners.

Noting that a previous study showed a higher risk of HIV-1 acquisition in women with bacterial vaginosis, Craig R. Cohen, MD, MPH, from the University of California San Francisco, and colleagues conducted a prospective study of 2,236 HIV-1 seropositive women and their male partners who were negative for HIV-1 from seven African countries. Every three months, vaginal swabs were obtained from the females and assessed for vaginal flora, and their male partners were tested for HIV-1.

During 24 months of follow-up, the researchers recorded 50 incident HIV-1 infections in men whose HIV-1 infected female partners had an evaluable vaginal Gram stain. The incidence of HIV-1 infection was significantly higher in men whose partners had bacterial vaginosis compared with normal vaginal flora (2.91 vs. 0.76 per 100 person-years; hazard ratio, 3.62). After taking various sociodemographic and clinical factors into account, the hazard ratio was 3.17.

“Given the high prevalence of bacterial vaginosis and the association of bacterial vaginosis with increased risk of both female HIV-1 acquisition and transmission found in our study, if this association proves to be causal, bacterial vaginosis could be responsible for a substantial proportion of new HIV-1 infections in Africa,” Cohen and colleagues conclude. “Normalization of vaginal flora in HIV-1-infected women could mitigate female-to-male HIV-1 transmission.”

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