Is Bacterial Vaginosis an STI? Groundbreaking Research Reshapes the Debate

A pervasive yet often misunderstood vaginal condition—bacterial vaginosis (BV)—may not be what we’ve always assumed. Emerging research suggests BV might actually qualify as a sexually transmitted infection (STI), a revelation that could radically shift the landscape of diagnosis and treatment.

That’s the compelling argument put forth by a team of researchers in a study recently published in the New England Journal of Medicine. Their findings have seismic implications, not just for how BV is classified but for who should be treated and which medical strategies might finally curb its stubborn recurrence.

BV, a condition marked by an overgrowth of disruptive bacteria in the vaginal microbiome, afflicts roughly 30% of reproductive-aged women in the U.S. Beyond discomfort, its repercussions can be severe: increased vulnerability to other STIs, heightened risk of pelvic inflammatory disease, and persistent recurrence despite treatment.

Typically, women diagnosed with BV undergo a one-week antibiotic regimen, either in oral or topical form. Yet, the condition boasts a staggering recurrence rate—nearly 80% of women experience reinfection within nine months.

Faced with these disheartening statistics, researchers decided to challenge conventional wisdom. What if, instead of treating only the woman, her male sexual partner was treated as well? Their results were groundbreaking: dual treatment significantly improved cure rates, suggesting that reinfection may stem from untreated partners.

“We, and others, have amassed substantial evidence indicating that BV and BV-associated bacteria are sexually transmitted,” explained study authors Lenka Vodstrcil and Catriona Bradshaw, esteemed researchers from Monash University and the Melbourne Sexual Health Centre, Alfred Health, in an email to Health.

What Is BV?

BV manifests when the natural balance of “good” and “bad” bacteria in the vagina is disrupted, according to the Centers for Disease Control and Prevention (CDC).

“The vaginal microbiome is typically populated by protective bacteria that support a stable and healthy environment. However, in BV, an overgrowth of disruptive bacteria destabilizes this delicate equilibrium,” explains Aparna Sridhar, MD, an associate clinical professor of obstetrics and gynecology at the David Geffen School of Medicine at UCLA.

While BV can be asymptomatic, those who do experience symptoms may notice:

• A thin, white or gray vaginal discharge
• Burning, itching, or discomfort in the vaginal area
• A pronounced fish-like odor, particularly post-intercourse
• Painful urination
• External vaginal irritation or itching

Why Isn’t BV Officially Labeled an STI?

Despite accumulating evidence, leading medical organizations, including the American College of Obstetricians and Gynecologists (ACOG), have yet to classify BV as an STI. The reason? A lingering ambiguity surrounds its exact cause.

Historically, BV was not categorized as an STI because it can, albeit rarely, develop in individuals who have never engaged in sexual activity. Moreover, men, who can harbor BV-associated bacteria, typically exhibit no symptoms, making it difficult to establish a direct causative link.

Nevertheless, research strongly indicates that sexual activity plays a significant role. Studies have detected BV-associated bacteria in men, both within the urethra and on penile skin, reinforcing the idea that partners may be reinfecting one another.

Previous clinical trials in the 1980s and 1990s attempted to treat both partners but yielded disappointing results. Notably, these studies only administered oral antibiotics to male participants, overlooking the potential efficacy of topical treatments.

“The mounting evidence suggesting BV is sexually transmitted was too substantial to ignore, necessitating a fresh approach to partner treatment,” Vodstrcil and Bradshaw stated. “We hypothesized that a dual-treatment strategy, targeting both oral and topical bacterial reservoirs, could be the missing piece.”

A New Approach: Treating Both Partners

The researchers recruited 164 monogamous heterosexual couples for their study, each with a female participant diagnosed with BV. The participants were divided into two cohorts: one in which only the woman received treatment, and another in which both partners were treated—men received both oral antibiotics and topical therapy.

The results were so striking that the study was halted early. Among women who underwent treatment alone, 63% experienced a recurrence of BV within 12 weeks. By contrast, in the group where both partners were treated, recurrence rates plummeted to 35%.

“Our trial conclusively demonstrated that reinfection from an untreated sexual partner is a major driver of BV recurrence,” the researchers asserted. “By expanding treatment to male partners, we’ve uncovered a straightforward strategy to significantly reduce BV’s persistent resurgence.”

However, the study’s scope had limitations—it focused exclusively on monogamous heterosexual couples, leaving questions about its applicability to individuals with multiple partners or those in same-sex relationships.

Additionally, the study was conducted in Australia, with most participants hailing from the Western Pacific and European regions. Given that BV prevalence varies based on geography and ethnicity, further research is needed to determine whether these findings hold universally.

Will This Research Transform BV Treatment?

While the findings mark a pivotal moment in BV research, Sridhar cautions that it’s premature to redefine BV as an STI outright.

“This study provides compelling evidence that treating male partners may reduce BV recurrence,” Sridhar acknowledged, “but it does not categorically establish BV as a sexually transmitted infection. If BV were a strict STI, we would not observe cases in individuals who have never been sexually active.”

Yet, Gale Burstein, MD, MPH, FAAP, professor of pediatrics at the Jacobs School of Medicine and Biomedical Sciences at the University at Buffalo and commissioner for the Erie County Department of Health, views the study as a game-changer.

“By significantly curbing BV recurrence through the treatment of male sexual partners, we now have substantial proof that BV-associated bacteria are transmitted sexually,” Burstein noted in an email to Health.

She also pointed out that healthcare providers routinely treat the sexual partners of patients with gonorrhea, chlamydia, and trichomoniasis to prevent reinfection—perhaps BV should be no different.

With the research in hand, Vodstrcil and Bradshaw are advocating for systemic change. They’ve launched an online platform to disseminate their findings, educate medical professionals, and empower women to discuss BV treatment options with their partners.

“We understand that asking asymptomatic men to take medication might seem perplexing,” they acknowledged. “But this study underscores a crucial point: treating BV isn’t just an individual concern—it’s a shared responsibility.”