Researchers say the drug-resistant form of the diarrhoeal infection is spreading faster than other types, and expect it to become more common in the coming years.
A sexually transmitted form of shigellosis is on the rise in the UK, and many of the bacteria tested show resistance to antibiotics, according to a recently published paper. Infectious diseases expert Julia Marshall wrote that its spread was happening “more rapidly” and “more intensely” than other versions of the illness, with the highest rates among men who have sex with men. England recorded 2,560 diagnoses of sexually transmitted shigella in 2025. The paper warns that the trend is likely to continue.
What the figures show
The 2025 total compares with 2,318 diagnoses in 2024 and 2,052 in 2023. London accounted for about 54% of the cases reported in 2025, the largest regional share.
Resistance is a particular concern. Among samples tested in 2025, 86% of Shigella sonnei isolates and 94% of Shigella flexneri isolates linked to likely sexual transmission were resistant to antibiotics. More than half of the tested S. sonneiisolates were classed as extensively drug-resistant. These percentages relate to the samples tested rather than to every diagnosed infection.
The paper warned: “In the coming years, it is likely that the spread of sexually transmissible drug-resistant shigellosis will increase.”
The 2025 outbreak
Researchers examining an outbreak detected in England in June 2025 identified 83 cases of drug-resistant shigella. Of these, 75 carried a particular antibiotic-resistance gene. Most of those affected were adult men, and none reported recent travel outside Europe. That suggests the outbreak was circulating through established transmission networks rather than being explained solely by travel abroad.
Questions over the cause
The paper asks what is behind the rise and suggests that people having sex while travelling internationally could be contributing. It recommends further research into the role of “local and international travel in spreading” the bacteria, in order to protect public health.
Research also indicates that sexually transmitted shigella is becoming established within domestic transmission networks. Travel may add to its spread, but infections can pass between people who have not been abroad.
Symptoms and transmission
Symptoms of shigellosis include severe diarrhoea, stomach cramps, fever, nausea and pain when passing stools. They typically begin one to four days after exposure. The infection has been fatal in extremely rare cases, normally involving patients with existing medical conditions.
Shigella is highly infectious and is not spread only through sex. It can also pass through contaminated food, water and surfaces. Hand-washing and good food hygiene normally help to prevent it, but the paper noted that the sexually transmitted form is harder to guard against because it is passed through faecal matter.
According to the NHS, sex that may involve contact with faeces can pass on the bacteria. This includes anal sex, oral sex involving contact with the anus, fisting, touching a condom or sex toy used for anal sex, and oral sex after anal sex.
Treatment and advice
Drug-resistant does not automatically mean untreatable. Many people recover without antibiotics, though severe infections may require hospital care. Resistance can complicate treatment because some strains are unaffected by several commonly used antibiotics.
The NHS advises people to contact their GP if they have symptoms of shigella or diarrhoea containing blood. Anyone with symptoms who thinks the infection was passed on during sex should contact their local sexual health service.
Health officials also recommend several precautions:
- washing hands thoroughly after sex
- changing condoms between anal and oral sex
- using barriers during oral-anal contact
- avoiding sexual activity until at least seven days after symptoms have stopped, if infected
