Can Bacterial Vaginosis Be Transmitted to a Sexual Partner?
Bacterial vaginosis is not a classic sexually transmitted infection, and treating male partners does not prevent recurrence or alter the clinical course in women. 1
The Nature of BV and Sexual Transmission
While BV is strongly associated with sexual activity, the evidence indicates it functions as a sexually enhanced disease rather than a traditional STI:
- Women who have never been sexually active are rarely affected by BV, establishing a clear link to sexual behavior 1
- BV is associated with having multiple sex partners, though it remains unclear whether this results from acquisition of a sexually transmitted pathogen 1
- The condition represents a disruption of normal vaginal flora where protective H₂O₂-producing Lactobacillus species are replaced by anaerobic bacteria, rather than infection with a single transmissible pathogen 2, 3
Evidence Against Classic Sexual Transmission
The strongest evidence that BV does not behave like a traditional STI comes from treatment studies:
- Treatment of male sexual partners has consistently failed to prevent BV recurrence in women, according to multiple CDC guidelines spanning decades 1, 2
- Male partners of women with BV are not symptomatic, and treating them does not alter the clinical course of BV during treatment or reduce relapse rates 1
- This lack of benefit from partner treatment is a key reason the CDC does not classify BV as exclusively an STD 1
Recent Contradictory Evidence
However, a 2025 randomized controlled trial directly contradicts these longstanding guidelines, showing that combined oral and topical antimicrobial treatment of male partners reduced BV recurrence from 63% to 35% within 12 weeks (absolute risk difference of -2.6 recurrences per person-year, P<0.001) 4. This trial was stopped early due to the clear benefit of partner treatment.
Sexual Behaviors and BV Risk
The relationship between sex and BV appears mechanical rather than infectious:
- Incident BV is significantly associated with exposure to new sexual partners (RR 1.74, P=0.03) and frequency of vaginal intercourse (RR 1.07, P=0.03) 5
- Condom use with occasional partners is protective (RR 0.80, P=0.003), suggesting mechanical factors play a role 5
- BV is common among women-who-have-sex-with-women, relating to non-coital sexual behaviors, further supporting that penetrative intercourse is not the sole mechanism 6
- The pathogenesis likely involves alkalinization of the vaginal environment during unprotected intercourse and mechanical transfer of perineal bacteria during any sexual activity 6
Clinical Implications
Based on the weight of guideline evidence, do not routinely treat male partners of women with BV 1, 2. The primary goals of BV treatment are to relieve vaginal symptoms in the affected woman and reduce risk for complications such as post-procedural infections and adverse pregnancy outcomes 1.
Common Pitfalls to Avoid:
- Do not counsel patients that BV is a sexually transmitted infection requiring partner notification like gonorrhea or chlamydia 1
- Do not assume absence of symptoms means absence of disease—up to 50% of women with BV are asymptomatic 1, 2
- Be aware that BV has a high recurrence rate (50-80% within one year) regardless of partner treatment in most studies, though the 2025 trial suggests this may be modifiable 2, 4
When to Consider Partner Treatment:
Given the 2025 trial results 4, consider discussing partner treatment with couples experiencing recurrent BV despite standard therapy, acknowledging this represents emerging evidence that contradicts established guidelines. The regimen used was metronidazole 400mg tablets and 2% clindamycin cream applied to penile skin, both twice daily for 7 days 4.