Why sexually transmitted diarrhea disease is becoming harder to treat in the US, and why Canada is also concerned about drug-resistant Shigella

A gut pathogen that causes diarrhea and vomiting is morphing into a dangerous and difficult-to-treat sexually transmitted infection (STI) is spreading in the United States, sparking concern among the health officials. Drug-resistant strains of a sexually transmissible bacterial infection that causes diarrhea and vomiting in the US are growing. According to a report in the Toronto Sun, Shigellosis, a severe intestinal infection caused by Shigella bacteria, is becoming harder to treat in the US. The treatment of sexually transmitted diarrhea disease is becoming tough due to increasing cases of extensively drug-resistant (XDR) strains of the gut pathogen.

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Why is sexually transmitted diarrhea spreading rapidly in the US?

An expert told the New York Post that the infection is spreading more through sex and later on becomes difficult to trace. In the United States, the shigella bacteria affects nearly half a million people and causes diarrhea with blood or mucus (the hallmark of a dysentery infection), stomach pain, cramps, fever and vomiting. If we look into the history, this highly contagious bug has mostly been spread through contaminated food or water during travel, and among young children in day care. However, now Shigella bacteria have emerged as a sexually transmitted infection as well. Shigella infections can make anyone sick, but they are now considered 'endemic' in some communities of gay, bisexual and other men who have sex with men (GBMSM).


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What is shigella bacteria?

Shigella is a nasty illness that can become life-threatening by dehydrating and depleting bodily fluids including blood, causing bacterial and septic shock, neurological complications, and internal bleeding and infection. The bacteria spreads through infected poop that gets into the mouth because of ill-washed hands, or swallowing tainted food or water. A minuscule amount, as few as 10 organisms, is enough to get you sick.

Children under the age of five are most likely to get infected by shigella bacteria. The kids can catch it from schools from other kids who are just starting to learn about keeping themselves clean. Travelers to places where sanitation standards are lower, and people experiencing homelessness are also at higher risk. Experts say shigella is “endemic” to these communities, meaning it’s constant and regularly present. Experts also believe that many people are not aware that Shigella can spready through sex and this might be the reason behind fuelling infections.

“Many men who have sex with men are unaware of the serious and increasing risk posed by sexually transmitted Shigella,” said Cambridge geneticist Kate Baker, a lead author on the July study.

The strains of shigella spread through sex are serious. Research shows that those who contracted shigella through sex were hospitalized for four to five days, on average.

“This isn’t just one form of sexually transmissible diarrhea,” Baker told Science Alert. “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.”

Prevention and treatment of Shigella infection

Many cases of shigella resolve on their own within a week, with the help of rest and fluids. But for serious infections, antibiotics might be used not only to shorten the illness but to reduce contagiousness, as well.

This is becoming harder as the strains become more resistant to antiobiotics. That’s why the CDC is urging more attention and development of prevention strategies. The emergence of XDR Shigellosis is concerning as it means the infection is caused by a strain of bacteria that has grown resistant to all five standard antibiotics used to treat it.

XDR Shigella infection also reported in Canada

Not just the United States, Canada has also reported cases of extensively drug-resistant (XDR) Shigella. According to a 2024 disease debrief by the National Collaborating Centre for Infectious Diseases (NCCID), Canada reported around 880 cases of shigellosis annually. The proportion of XDR Shigella cases increased from 1% in 2018 to 6.6% in 2022.

In September 2022, an outbreak in Montreal infected 56 people, most of them sexually active men. Of those cases, 25 involved a multidrug-resistant strain of the bacteria. The NCCID also highlighted outbreaks affecting people experiencing homelessness. These included an outbreak that sickened 63 people in Calgary in July 2024 and another in Vancouver’s Downtown Eastside in 2021.