One of the most common causes of food poisoning in the United States is becoming a sexually transmitted disease. Shigella, the bacteria behind shigellosis — a severe diarrheal illness — has long been blamed on contaminated food and water. But a growing body of research shows it is spreading rapidly through sexual contact, with drug-resistant strains surging among certain populations in the US.
A study published in the CDC journal Emerging Infectious Diseases put striking numbers on the trend. Danish surveillance data from 2010–2018 found that men who have sex with men had 74 times higher odds of Shigella infection than controls — while Salmonella rates showed no significant difference, ruling out the theory that MSM simply eat more undercooked food. Campylobacter infection odds were 14 times higher in the MSM group.
A large UK study told a similar story. Researchers at Cambridge University, working with the UK Health Security Agency, analyzed 3,514 Shigella samples collected across Britain from 2004 to 2020: about a third came from men who have sex with men. More than half of all UK Shigella infections are now estimated to be sexually transmitted. Cases began climbing dramatically around 2010 after decades of little growth, a rise researchers link partly to dating apps and "chemsex" parties — group-sex events involving stimulant drugs.
Shigella is extraordinarily contagious: as few as 10 organisms can cause disease, compared with more than 1,000 for Salmonella. Transmission usually happens through direct or indirect mouth-to-anus contact, letting trace amounts of fecal matter pass the bacteria between partners.
The harder problem is resistance. CDC data show extensively drug-resistant (XDR) Shigella went from 0% of US cases in 2011 to 8.5% in 2023. About 450,000 Americans contract Shigella each year; among XDR patients the median age was 41, 86.2% were male, and more than a third ended up hospitalized. First-line antibiotics — azithromycin, ciprofloxacin and others — are losing their power against these strains.
"Although anyone can get Shigella, we see higher rates among gay, bisexual and other men who have sex with men, in part because it can be passed through sexual contact," said Dr. Jason Zucker of Columbia University Medical Center. Infectious-disease specialist Dr. William Schaffner of Vanderbilt warned that the summer social season demands extra caution: "Not only are we concerned about HIV and other sexually transmitted infections, but now we have to add XDR shigellosis to the list."
California's public health department issued a flyer in May with a memorable line: "Communication is sexy, diarrhea isn't — talk with your partners about any recent diarrhea, and wait to have sex to prevent the spread."
Researchers add another warning: Shigella's resistance genes can potentially jump to other gut bacteria, multiplying the danger. There is no vaccine. The practical advice from experts: seek care promptly for diarrhea and fever, use lab testing to guide treatment, and report XDR cases quickly — so each outbreak can be stopped before it spreads.