Shigella, the gut bacterium behind roughly 450,000 US shigellosis cases a year, is now spreading significantly through sexual contact rather than just contaminated food, water, or daycare settings. A recent CDC analysis of nearly 17,000 Shigella isolates found that versions resistant to five commonly used antibiotics rose from 0 percent of samples in 2011 to 8.5 percent by 2023, with the vast majority infecting adult men who had not traveled internationally.

According to CDC data cited by the Toronto Sun, of 492 XDR cases with demographic details, 86.2 percent were men and 96.1 percent were adults 18 or over; among those with known HIV status, 46.6 percent had HIV co-infection, and over a third of drug-resistant patients were hospitalized. Cambridge geneticist Kate Baker told ScienceAlert that up to a third of sexually transmitted Shigella patients were hospitalized for four to five days on average, and UKHSA testing in 2025 found 86 percent of S. sonnei and 94 percent of S. flexneri samples showed antibiotic resistance.

Baker warned the 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,' and that patients who contract Shigella through sex likely need different treatment than travel-acquired cases. CDC epidemiologist Naeemah Logan called it 'a very concerning pattern... among vulnerable populations' and part of a broader global pattern. One suspected driver is 'bystander resistance,' where antibiotics prescribed for other infections breed resistance as a side effect — ScienceAlert notes that when UK gonorrhea guidelines stopped recommending azithromycin, azithromycin resistance in Shigella slowed.

Clinicians are being urged to ask dysentery patients about sexual transmission and screen for other STIs, as consultant Daniel Richardson at University Hospitals Sussex advised. The CDC recommends washing hands, genitals and sex toys with soap and water before and after sex, and using barriers like condoms and dental dams; the California Department of Public Health simply advises not having sex with anyone who has had diarrhea in the past two weeks. Canada's NCCID reports XDR cases rose from 1 percent to 6.6 percent between 2018 and 2022, signaling the trend is not confined to the US.