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• Posted March 10, 2025

Common Vaginal Infection Should Be Treated as an STI, Study Says

A common vaginal infection that affects nearly 1 in 3 women worldwide should be reclassified as a sexually transmitted infection (STI), a new study suggests.

Bacterial vaginosis (BV) is now treated as a women’s health issue, but researchers reported March 5 in The New England Journal of Medicine that treating male partners along with female patients reduced recurrence rates by 60%.

The findings suggest BV is sexually transmitted, meaning that treating women only may not be enough to prevent reinfection.

“Our trial has shown that reinfection from partners is causing a lot of the BV recurrence women experience, and provides evidence that BV is in fact a STI,” senior author Catriona Bradshaw, a professor at the Melbourne Sexual Health Center at Monash University in Australia, told CNN in an email.

BV occurs when the balance of bacteria in the vagina is disrupted. Symptoms can include itching, pain while urinating, unusual vaginal discharge and an unpleasant odor, though many women have no symptoms at all.

BV is more than just uncomfortable -- it can also pose serious health risks if left untreated.

It increases the risk of contracting HIV and other sexually transmitted infections, according to the World Health Organization (WHO).

It can also cause pelvic inflammatory disease, which can result in infertility.

“We see very significant changes in a range of inflammatory markers, inflammatory cells and bacterial enzymes and products that result in damage to the epithelium -- the lining of the reproductive tract,” Bradshaw added.

Doctors typically prescribe a week-long course of antibiotics to treat BV. However, research shows that for half of all women, the infection returns after treatment.

In an Australian clinical trial, 164 monogamous couples were divided into two groups. In one group, both partners were treated with oral antibiotics, while men also applied a topical antibiotic to their penis twice daily. 

In the other group, only the women were treated.

The results were clear: Women whose partners were also treated were 60% less likely to experience reinfection compared to those whose partners weren't treated.

“The bacteria that cause BV can be located in men, especially in penile skin and also in the urethra,” lead author Lenka Vodstrcil, a senior research fellow at the Melbourne center, said in a news release. 

“This suggests that BV is probably sexually transmitted, and that is why so many women get it back again after treatment,” she added.

Researchers ended the study early because the benefits of treating both partners became obvious so quickly.

If BV is reclassified as an STI, it could change how doctors approach treatment, requiring them to inform male partners of their role in the infection happening again.

This would be a “paradigm shift” and would require doctors to encourage a woman’s male partner to share their responsibility for transmission and treatment, according to an editorial published alongside the study.

“It will also require a willingness of male partners to commit to taking both oral and topical medications, once notified by their female partner that she has bacterial vaginosis and that it is probably sexually transmitted,” the editorial pointed out. 

It was co-written by Dr. Christina Muzny, a professor of infectious disease at the University of Alabama at Birmingham, and Dr. Jack Sobel, a professor of infectious disease at the Wayne State University School of Medicine in Detroit.

Researchers reported that male study participants had no issues completing the antibiotic course.

“We have now used this medication in close to 300 men and have not had any report that side effects from the medication would stop them from taking it,” Bradshaw noted.

The Melbourne center has already changed its treatment protocols to include male partners when BV is detected. Researchers have also developed a website for healthcare professionals and couples interested in treating both partners.

“Changes in national and international treatment guidelines always take time, so we felt an obligation to provide accurate online and downloadable information,” Bradshaw concluded.

More information

The U.S. Centers for Disease Control and Prevention has more on about bacterial vaginosis.

SOURCE: CNN, March 6, 2025