Women who tested positive for bacterial vaginosis were more than three times as likely to have a sexually transmitted infection at the same time, laboratory data on more than 1.5 million US women show. Existing guidance already supports testing for both, and treating male partners has been shown to improve cure rates.
Among US women who tested positive for bacterial vaginosis (BV), 12.0% also had a sexually transmitted infection (STI). Among women who tested negative for BV, 3.8% did.
Scientists at Quest Diagnostics and Hologic drew those figures from laboratory tests on more than 1.5 million women aged 15 and over. Their analysis, published in O&G Open, covers testing between 2022 and 2024.
BV is a common imbalance of the bacteria normally found in the vagina. It can cause an unusual discharge and a strong odour, although many women have no symptoms.
Gonorrhoea, trichomoniasis and chlamydia
After adjustment, BV was linked to 3.8 times the odds of gonorrhoea and 3.6 times the odds of trichomoniasis. It was also linked to 2.8 times the odds of chlamydia and 1.9 times the odds of Mycoplasma genitalium, a less well-known bacterial STI.
Thrush, the yeast infection known medically as vulvovaginal candidiasis, showed no link to STIs when it occurred alone. Some 38.7% of the women tested positive for BV and 28.5% for candidiasis, and 10.8% had both.
Quest and Hologic both sell diagnostic tests, including the kind of multi-infection molecular testing the study supports. All the data came from one national laboratory, and the researchers had no information on sexual history or other risk factors. The study is cross-sectional, so it shows that the infections occurred together without showing that one caused the other.
O&G Open is a peer-reviewed companion journal to Obstetrics & Gynecology, published by the American College of Obstetricians and Gynecologists, according to Contemporary OB/GYN.
Testing for STIs at the same visit
BV affects between 23% and 29% of women of reproductive age worldwide, according to a review cited by the World Health Organization. WHO states that BV increases the risk of acquiring HIV and of acquiring and transmitting other STIs.
The US Centers for Disease Control and Prevention already advises testing. Its 2021 treatment guidelines, which remain current, state that “all women with BV should be tested for HIV and other STIs”. The new data add large-scale support to that advice.
In England, the NHS says a sexual health clinic will want to confirm BV and rule out an STI. It notes that “many sexual health clinics offer a walk-in service, where you do not need an appointment”. Women diagnosed with BV anywhere can ask whether they have also been tested for chlamydia and gonorrhoea.
Most STIs cause no symptoms, according to WHO’s STI fact sheet. It estimates that more than 1 million curable STIs are acquired every day among people aged 15 to 49. Gonorrhoea and chlamydia are major causes of pelvic inflammatory disease and infertility in women.
Treating partners to stop BV returning
BV often comes back within a few months, the NHS says. Researchers in Melbourne tested one answer. In the StepUp trial, published in the New England Journal of Medicine in March 2025, male partners were treated alongside women.
That approach more than doubled the likelihood of BV cure compared with treating women alone, according to Monash University. Its team has since published resources for clinicians and pharmacists who want to offer partner treatment.
Researchers from Monash and The Alfred hospital won a 2026 Eureka Prize for the work. “Our trial proved that male partners are key to improving BV cure,” said Dr Lenka Vodstrcil of Monash University, in a Monash statement.
This article is for information only and does not replace advice from a qualified health professional.
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