A common condition affecting up to one in four women should be reclassified as a sexually transmitted infection, experts say, after new evidence suggests sex plays a key role in driving it.
Bacterial vaginosis – known as BV – occurs when there is an imbalance in the natural bacteria in the vagina.
It is often mild, typically causing discharge or a distinctive odour, and around half of women experience no symptoms at all.
But the condition is far from harmless. It has been linked to an increased risk of sexually transmitted infections including chlamydia and gonorrhoea, as well as pregnancy complications such as miscarriage and preterm birth.
Now, leading gynaecologists say the case for classifying BV as an STI is strengthening, after studies showed that treating male partners alongside women significantly improves outcomes.
The findings suggest the condition may be sexually transmissible – even though men themselves do not develop symptoms.
‘The traditional argument against calling bacterial vaginosis an STI is that it stems from an overgrowth of endogenous flora rather than a single external pathogen, but this is becoming increasingly difficult to defend,’ said Valentina Milanova, an expert in public and gynaecological health.
BV is typically treated with antibiotics, but it is notoriously difficult to eradicate. Around half of women experience a recurrence within six months.
Experts are calling for BV to be treated like an STI, with both men and women being treated against the infection
One reason is that while men cannot develop BV, they can carry BV-associated bacteria – meaning untreated partners may reintroduce the imbalance.
Despite this, partners are not routinely treated in the UK, potentially exposing women to repeated infection and increasing their vulnerability to more serious conditions, including HIV.
Experts are now calling for BV to be managed in the same way as an STI, with both partners treated to break the cycle of reinfection.
In countries such as the US, Canada and Australia, BV is already managed within sexual health frameworks in line with World Health Organisation guidance.
But the UK has lagged behind.
‘The British Association for Sexual Health and HIV’s guidelines date back to 2012 and have not been updated to reflect current evidence,’ Ms Milanova said.
‘As a result, clinicians are not routinely treating partners, notifying contacts or screening systematically – leaving many women stuck in a cycle of recurrence that affects their overall wellbeing.’
She added: ‘The consequences extend well beyond discomfort. Recurrent BV significantly increases susceptibility to HIV, HPV, chlamydia, gonorrhoea and urinary tract infections.
‘It is also associated with serious reproductive risks, including preterm birth and miscarriage.’
The need for better prevention is becoming increasingly clear.
Separate research has also suggested that restoring so-called ‘good’ bacteria in the vaginal microbiome could help reduce recurrence.
In a study of 90 women with BV, researchers from Mass General Brigham and the Vaginal Microbiome Research Consortium found those who took a daily probiotic containing beneficial bacteria after antibiotics were less likely to experience a recurrence.
Some participants only needed to take the treatment for a few days for the bacteria to establish themselves, helping make the vaginal environment more acidic and less hospitable to harmful microbes.
Unlike antibiotics, which clear infection, the approach aims to rebuild a protective microbiome.
Researchers say this could have wider benefits, including potentially reducing the risk of HIV in high-prevalence settings.
There are also simple steps that may help reduce the risk of BV or prevent it returning, including avoiding perfumed products, douching or vaginal deodorants, and washing with water or mild soap.
Smoking, having a new sexual partner and using an intrauterine device (IUD) have also been linked to a higher risk, as these can disrupt the natural balance of bacteria in the vagina.
