Drug-Resistant Shigella Is Spreading Through Gay Sexual Networks, Study Finds
A new Cambridge University study has found that sexually transmitted Shigella, the bacteria behind bloody diarrhoea and dysentery, is spreading fast through sexual networks of gay and bisexual men in the UK and building drug resistance faster than any other form of the disease.
The research, published in The Lancet Infectious Diseases, used the same genetic tracking methods deployed during the covid pandemic, only this time to follow bacteria instead of a virus.
Between 2015 and 2020, sexually transmitted Shigella in the UK grew 15% faster year on year than strains picked up through overseas travel, contaminated food, or nursery outbreaks.
By the end of that period, more than 70% of sexually transmitted strains had become resistant to at least one clinically relevant antibiotic, compared with 40% of non-sexually transmitted strains. The UK Health Security Agency recorded 2,560 cases of sexually transmitted Shigella in 2025, more than half of them in London.
How Does It Spread So Easily?
Shigella only needs around ten bacterial cells to cause infection, one of the most contagious pathogens around. It passes through direct or indirect contact between the mouth and anus, so practices like rimming and group sex at chemsex parties can pass it on quickly.
Researchers pointed to hookup apps as one likely factor behind the sharp rise in cases since 2010.
Professor Kate Baker, the study’s senior author from Cambridge’s Department of Genetics, said many gay and bisexual men are unaware of the risk.
“This isn’t just one form of sexually transmissible diarrhoea,” she said. “This is multiple overlapping variants emerging that are all quickly becoming resistant to the drugs we use to treat them.”
Earlier research from Baker’s team found that up to a third of people with sexually transmitted Shigella end up hospitalised, and around two thirds of gay and bisexual men with the infection are also living with another sexually transmitted infection (STI), including HIV.
It’s Not Just Happening in the UK
Australia has seen the same pattern. SA Health confirmed six cases of the same multidrug-resistant Shigella strain among gay, bisexual and other men who have sex with men in South Australia in the first months of 2026, after five cases were recorded across 2025. Australia’s Centre for Disease Control also lists gay and bisexual men among the groups most at risk of the infection nationally.
Marc Tweed from the Terrence Higgins Trust in Brighton said the exact drivers are still being worked out.
“Studies have linked transmission with dense sexual networks, multiple partners, sexualised drug use, PrEP use and concurrent sexually transmitted infections,” he said. “But these are associations, not proof that any one behaviour alone is driving the increase.”
What To Do If You Think You’ve Had It
Had an unexplained stomach bug recently that you brushed off as food poisoning? It might be worth a second look. Health experts recommend holding off on sex for two weeks after recovering from a bout of diarrhoea, telling your doctor about your sexual history if you seek treatment, and asking for a full sexual health screen while you’re there.
Shigella isn’t part of a standard STI panel, so it won’t turn up unless you specifically ask for it. At DNA, we’d rather you know that before your next hookup than after.
