TUESDAY, June 26, 2012 (HealthDay News) -- HIV-positive women with bacterial vaginosis, a disruption in the normal balance between healthy and harmful bacteria in the vagina, are three times more likely to pass HIV on to male sexual partners, according to a new study.
Researchers from the University of California-San Francisco, said new developments in treatment for bacterial vaginosis could not only improve women's health, but also help reduce HIV transmission rates.
"Previous research has shown that bacterial vaginosis can increase women's risk of becoming infected with HIV by as much as 60 percent," lead study author Dr. Craig Cohen, professor of obstetrics, gynecology and reproductive sciences, said in a university news release. "Our study is the first to show that the risk of transmitting HIV is also elevated."
In conducting the study, the researchers examined the link between bacterial vaginosis and female-to-male HIV transmission risk among more than 2,200 HIV-positive African women and their HIV-negative male partners.
After taking into account the participants' socio-demographic factors, sexual behavior, sexually transmitted infections, pregnancy and women's blood levels of HIV -- as well as whether their male partners were circumcised -- the researchers found bacterial vaginosis was still associated with a significantly higher risk for female-to-male transmission of HIV.
The researchers say it remains unclear exactly how bacterial vaginosis affects transmission rates.
"We looked at the increased shedding of HIV in the genital tract, but that was not sufficient to explain the increased risk of female-to-male HIV transmission," Cohen said. "It is also possible that bacterial vaginosis causes inflammation, and that could be a factor."
It is possible that sharing genital tract organisms between women and men could explain the higher HIV transmission risk, the researchers suggested.
"Our findings point to the need for additional research to improve the diagnosis and treatment of bacterial vaginosis, which is extremely common in sub-Saharan Africa, the region of the globe with the highest burden of HIV," Cohen said.
The study, funded by the Bill & Melinda Gates Foundation, was published June 26 in the journal PLoS Medicine.
The U.S. Centers for Disease Control and Prevention provides more information on bacterial vaginosis.