A sexually transmitted infection that causes severe, bloody diarrhea has become “endemic” in some communities, with drug-resistant strains spreading rapidly and experts warning the illness is becoming “close to untreatable.”
Behind the alarming trend is Shigella, a group of bacteria that causes an intestinal infection known as shigellosis, which can trigger painful stomach cramps, fever and diarrhea that sometimes contains blood.
How does Shigella spread?
Unlike infections that require direct sexual contact to spread, Shigella can infect someone who accidentally swallows even a microscopic amount of contaminated fecal matter.
According to the Centers for Disease Control and Prevention (CDC), “Shigella germs are in poop,” and can spread through unwashed hands, contaminated food or water, and sexual activities involving contact with fecal matter.
Children younger than five are particularly vulnerable, while international travelers and people experiencing homelessness also face increased risks.
However, researchers are increasingly concerned about infections among gay, bisexual and other men who have sex with men – where Shigella is considered “endemic” – as the bacteria can “spread easily from person to person through fecal-oral transmission or sexual contact.”
‘Increasing risk’
A July 2026 study published in The Lancet Infectious Diseases examined infections in England and found that sexually transmitted strains spread approximately 15% faster annually between 2015 and 2020 than those associated with other transmission routes.
Cambridge University geneticist Kate Baker, one of the study’s authors, warned that many people remain unaware of the danger.
“Many men who have sex with men are unaware of the serious and increasing risk posed by sexually transmitted Shigella,” she said, according to the New York Post.
But the growing number of infections is only part of the problem, as researchers have identified several strains that are becoming increasingly resistant to treatment.
‘Close to untreatable’
According to an April 2026 CDC report, the proportion of extensively drug-resistant Shigella samples in US surveillance rose from 0% during 2011–2015 to 8.5% in 2023.
These strains are “extensively drug-resistant,” leaving doctors with fewer established treatment options.
“This disease has gone from being relatively treatable with off-the-shelf drugs to being close to untreatable over the course of the last decade or so,” Baker warned.
And the growing resistance isn’t limited to a single strain.
“This isn’t just one form of sexually transmissible diarrhea,” Baker told ScienceAlert.
“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.”
Although many infections resolve without complications, severe cases can require hospitalization, particularly when dehydration becomes dangerous.
Symptoms and treatment
Symptoms typically appear within one or two days of exposure and can last about a week.
According to the CDC, common warning signs include:
- Diarrhea, which may contain blood or last longer than three days
- Fever
- Abdominal pain and cramping
- Feeling an urgent need to poop even when the bowels are empty
Most people recover within a week, although doctors may prescribe antibiotics for more serious infections.
However, drug-resistant strains can complicate treatment, making it important for doctors to determine which medications are likely to work.
Anyone experiencing bloody diarrhea, severe symptoms or signs of dehydration should seek medical attention immediately.
Were you aware that a serious intestinal infection could spread through sexual contact? Please let us know your thoughts in the comments, and share this story to help raise awareness!
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