BV explained: why it’s now treated more like an STI

Bacterial vaginosis, or BV, is the most common cause of unusual vaginal discharge — and one of the most frustrating, because it so often comes back. For decades it was thought of as a simple imbalance that had nothing to do with sex. That view is now changing: strong new evidence shows BV can be sexually transmitted, and that treating a partner can stop it recurring. Here’s what BV is, why the thinking has shifted, and what it means for getting rid of it for good.

What is BV?

The healthy vagina is home to a community of bacteria dominated by lactobacilli, which keep it slightly acidic and help hold other microbes in check. BV happens when that balance is disrupted — lactobacilli decline and a mix of other bacteria (such as Gardnerella) overgrow. It isn’t a single “germ” so much as a shift in the whole ecosystem.

BV is extremely common: it’s the leading cause of abnormal discharge in women of reproductive age, and many women will have it at some point. It is not thrush — thrush is a yeast overgrowth with different symptoms and a different treatment — and the two are often confused. If itch and soreness are your main symptoms, see thrush instead.

What are the symptoms of BV?

BV can be completely silent, but when it causes symptoms the classic ones are:

• a thin, greyish-white discharge
• a distinctive “fishy” odour, often stronger after sex
• discharge that may seem more noticeable than usual.

Tellingly, BV usually does not cause itching, soreness or irritation — those point more towards thrush or another cause. The odour is often the symptom women notice most, and it’s a common reason for seeking help. It’s worth saying plainly: BV is a bacterial imbalance, not a sign of poor hygiene, and washing more (or using douches or scented products) tends to make it worse, not better.

Is BV a sexually transmitted infection?

This is where things have genuinely shifted. For a long time BV was classed as not an STI, largely because it can occur in women who have never been sexually active, and because treating male partners didn’t seem to help. But BV has always had STI-like features: it’s strongly linked to sexual activity, to having a new or multiple partners, and to not using condoms.

The honest position today is that BV sits somewhere in between. It isn’t a classic infection passed on like chlamydia, but for many women sexual activity clearly plays a role in getting it and in it coming back. Recent research has pushed that understanding much further.

Why the thinking is changing

The turning point was a landmark Australian trial, led from Melbourne and published in the New England Journal of Medicine in 2025. It tested something simple: when a woman with BV is treated, does also treating her male partner reduce how often BV comes back?

The results were striking enough that the trial was stopped early. Among couples where only the woman was treated, BV recurred in about 63% within 12 weeks. Where the male partner was also treated — with oral antibiotics plus a topical cream — recurrence fell to about 35%. In other words, treating the partner roughly halved the recurrence rate.

That’s powerful evidence that, at least in couples, BV can behave like a sexually transmitted condition: partners can carry the bacteria and effectively re-seed the infection. It’s why BV is increasingly being managed more like an STI — considering the partner, not just the individual — even though it isn’t formally reclassified as one. Guidance in this area is actively evolving, so partner treatment is something to discuss with your doctor rather than assume.

Why BV matters beyond the symptoms

BV is sometimes dismissed as just a nuisance, but it’s worth taking seriously, because the disrupted vaginal environment has knock-on effects:

• it makes the genital tract more susceptible to STIs, including chlamydia, gonorrhoea and HIV
• it’s associated with a higher risk of pelvic inflammatory disease
• in pregnancy, it’s linked to preterm birth and other complications, so it deserves particular attention if you’re pregnant.

None of this is cause for alarm, but it’s the reason BV is worth diagnosing and treating properly rather than living with, especially if it keeps returning.

How BV is diagnosed and treated

Diagnosis is straightforward. It’s usually confirmed with a vaginal swab — often self-collected — sometimes alongside a quick look at the discharge. Because BV symptoms overlap with thrush and with some STIs, testing rather than guessing is the reliable way to know what you’re treating; our BV test makes that simple.

Treatment is with antibiotics, either as tablets or a vaginal gel — most commonly metronidazole or clindamycin. Symptoms often settle within days. A few practical points help:

• finish the full course, even once symptoms improve
• avoid alcohol during and just after metronidazole, as the combination can cause nausea
• skip douching and scented washes, which disrupt the balance further.

Why BV comes back — and what helps

The most frustrating thing about BV is recurrence: even after successful treatment, it returns within a year for a large proportion of women. Part of the reason, as the new evidence suggests, is re-exposure through a partner. That’s why the conversation is moving beyond “treat and hope” towards strategies that address the underlying pattern — including, for some couples, treating the partner as well, and looking at practical steps like condom use. If your BV keeps coming back, that’s a good reason to see a doctor who can look at the bigger picture rather than just repeating the same short course.

When to see a doctor

It’s worth getting checked if you have a new or unusual discharge or odour, if symptoms don’t settle with treatment, if BV keeps returning, or if you’re pregnant. Because the symptoms overlap with other conditions, a proper diagnosis saves you treating the wrong thing. A Specialist GP can confirm what’s going on, prescribe the right treatment, and — importantly for recurrent BV — talk through the newer, partner-inclusive approaches to keeping it from coming back.

The bottom line: BV is common, treatable, and no reflection on hygiene — but it’s no longer seen as purely an internal imbalance. For many women, sex plays a real role, and the latest evidence shows that treating a partner can dramatically cut recurrence. If BV is a recurring problem for you, it’s well worth a fresh conversation with a doctor.