Experts warn cases of sexually transmitted gut infection are spreading rapidly in the UK
Sexually transmitted cases of shigella - a bacterial gut infection - are spreading rapidly in the UK, with experts warning of a distinct public health threat’.
Researchers have found that sexually transmitted cases of shigella, which causes diarrhoea, stomach cramps and fever, are not only spreading quickly but also becoming increasingly resistant to antibiotics.
Shigella is the bacteria behind dysentery, and is most commonly found in faeces (poo) and contracted through eating contaminated food.
However, it can also be transmitted during sexual activity.
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Sexually transmitted strains such as shigella sonnei and shigella flexneri mostly impact gay and bisexual men.
Earlier this year, UKHSA issued a warning about ‘sharp rise’ in sexually transmitted shigella in 2025 with 2,560 recorded cases last year, up from 2,318 in 2024 and 2,052 in 2023.
Now, a newly published study led by the University of Cambridge alongside UKHSA has found that sexually transmitted cases of the infection spread much faster in terms of distance compared to other strains.
The team analysed 3,514 samples of shigella from people over the age of 16 in the UK between 2004 and 2020.
They found that over two and a half years, sexually transmitted shigella strains spread more than twice as fast, averaging 117km in distance compared to 46km for non-sexually transmitted strains.
Researchers said the findings, published in the Lancet Infectious Diseases journal, show ‘the distinct and intensifying sexual transmission of shigellosis, highlighting the urgent need to address sexually transmissible shigellosis as a distinct health threat’.
Professor Kate Baker, from the University of Cambridge's Department of Genetics, said: “Many men who have sex with men are unaware of the serious and increasing risk posed by sexually transmitted shigella.
“Sexual infection is now a sustained part of shigella transmission in the UK. It is vital that this message reaches the communities most affected, so we can help to prevent the spread.
“Sexually transmissible shigellosis needs to be treated as a distinct public health threat, requiring different surveillance, prevention, and treatment strategies.”
Researchers estimate that more than half of all shigella infections in the UK are now sexually transmitted.
The study also found that around 70 percent of sexually transmitted shigella strains were resistant to at least one antibiotic, compared to 40 percent of non-sexually transmitted cases.
“This isn’t just one form of sexually transmissible diarrhoea," Professor Baker said.
"This is multiple overlapping variants emerging that are all quickly becoming resistant to the drugs we use to treat them. It’s highly likely that if you contracted your shigella through sex you require different treatment to someone who contracted it through travel.”
Offering advice on what to do if you think you may have shigella, Professor Baker added: “Some advice is obvious, but needs hammering home.
"If you start to feel unwell, or are recently recovering from a scary bout of diarrhoea, do not engage in sexual activity until two weeks after you're fully recovered, mention your sexual history to your doctor if you seek medical care, and ask about having a full sexual health screen."
In 2025, most diagnoses of sexually transmitted Shigella were seen in London (54 percent), followed by Thames Valley (six percent) and Surrey and Sussex (six percent).
Claire Reid