ScienceNot yet confirmed elsewhere1 publisher2 min readPublished
CDC finds 8.5% of 2023 US Shigella samples resisted five common antibiotics
The CDC reported in April 2026 that 8.5 percent of 2023 US Shigella samples resisted five common antibiotics, up from zero in 2011 through 2015. Because the infection mimics food poisoning, a sexual history can decide which treatment works.
The Scientist · Science desk
What happened
- The CDC counted 510 extensively drug-resistant isolates among the nearly 17,000 US Shigella samples collected between 2011 and October 2023.
- Among the 258 patients whose hospitalization status was recorded, about four in ten had been admitted, and the report recorded no deaths.
- A July study in The Lancet Infectious Diseases found UK strains tied to sexual transmission spread farther and formed more infection chains than other locally acquired strains.
- In the US samples where age and sex were recorded, most patients were adult men.
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Why it matters
- constraint The US data cannot show how much of the resistant rise is sexual spread: case records rarely noted sexual contact, and some of the increase may come from changes in testing.
- decision For severe or persistent diarrhea, a recent sexual history can change which test a clinician orders and which antibiotic they try.
- exposure Someone who feels better can still shed Shigella for up to two weeks, so the CDC advises waiting two weeks after diarrhea ends before sex.
- precedent UK health authorities advise anyone diagnosed with Shigella to be screened for other sexually transmitted infections.
Shigella is a gut infection. It spreads when tiny amounts of fecal matter reach the mouth, which during sex can happen through direct contact or on hands [9]. Most people recover without antibiotics; the resistance matters only for the minority who need treatment [10].
Measured across the whole collection period, the extensively-drug-resistant share is about 3 percent: 510 of the nearly 17,000 US samples gathered since 2011 [11][24]. The 8.5 percent for 2023 is the recent, higher slice.
The sexual-transmission signal comes from the UK. A study published in July in The Lancet Infectious Diseases, led by Cambridge's Kate Baker, examined more than 3,500 Shigella sonnei samples collected between 2004 and 2020 [2][3]. The team could not confirm how any individual was infected, so it counted men aged 16 to 60 with no recent travel to higher-risk regions as likely sexual transmission [4]. The route is inferred from age, sex and travel, not confirmed case by case.
"This is multiple overlapping variants emerging that are all quickly becoming resistant to the drugs we use to treat them," Baker said in a press release [17]. She added: "It's highly likely that if you contracted your Shigella through sex you require different treatment to someone who contracted it through travel" [18].
The study also connected Shigella's resistance to how gonorrhea is treated. In a person carrying both infections, an antibiotic given for the gonorrhea can kill the Shigella that are susceptible to it and leave the resistant ones to spread, an effect the authors call bystander resistance [19]. The clearest evidence came from a change in policy: when UK guidelines stopped recommending azithromycin for gonorrhea, Shigella strains resistant to azithromycin lost some of their spreading advantage [20].
What to watch
- Whether US case records start capturing sexual history, which would let surveillance measure the sexual-transmission rate directly.
- Whether US treatment guidance begins to differ by likely route of infection, as Baker suggests it should.
- Whether other countries see their gonorrhea prescribing reflected in Shigella resistance, as the UK azithromycin change was.
Clarity's read
What the record supports and how the coverage leans. The claims behind it follow.
Reality
- Evidence55
- Adoption
- Insufficient
- Hype gap+25
- Incentives
- Insufficient
- Confidence50
Claim ledger
Ranked by verification strength, evidence, and original report placement.
- [1]
A July study in The Lancet Infectious Diseases found that in the U.K., strains linked to sexual transmission spread farther and formed more chains of infection than other homegrown strains.
- [2]
The Cambridge team looked at more than 3,500 Shigella sonnei samples collected in the U.K. between 2004 and 2020.
- [3]
Kate Baker is the senior author of the U.K. study.
- [4]
Because they couldn't confirm how each person was infected, the team treated cases in men aged 16 to 60 with no recent travel to certain higher-risk regions as likely sexually transmitted.
- [5]
Infections in that group spread over greater distances and passed between people more intensely than other infections acquired within the U.K.
- [6]
A CDC report published in April 2026 found that 8.5 percent of U.S. Shigella samples analyzed from 2023 resisted five commonly used antibiotics.
- [7]
None of the U.S. Shigella samples from 2011 through 2015 resisted those five antibiotics.
- [8]
Because Shigella's symptoms look so much like food poisoning, the infection is easy to misread.
- [9]
Shigella causes diarrhea, fever and cramps and spreads when tiny amounts of fecal matter reach the mouth, which during sex can occur through direct contact or contaminated hands.
- [11]
Across nearly 17,000 samples collected between 2011 and October 2023, 510 met the CDC's definition of extensively drug-resistant.
- [13]
Of the 258 patients with known hospitalization status, about 4 in 10 had been hospitalized.
- [15]
The records often lacked information about sexual contact, leaving researchers unable to tell how quickly Shigella was spreading through sex across the U.S.
- [16]
Changes in testing may account for some of the rise in resistant samples.
- [17]
This is multiple overlapping variants emerging that are all quickly becoming resistant to the drugs we use to treat them.
- [18]
It's highly likely that if you contracted your Shigella through sex you require different treatment to someone who contracted it through travel.
- [19]
In someone carrying both infections, an antibiotic prescribed for gonorrhea can give resistant Shigella bacteria a better chance of surviving and spreading while bacteria susceptible to the drug are killed, an effect the authors call bystander resistance.
- [20]
When U.K. guidelines stopped recommending azithromycin for gonorrhea, Shigella strains resistant to that drug lost some of their advantage in spreading.
- [21]
The CDC recommends waiting at least two weeks after diarrhea ends before having sex, because people can keep passing Shigella in stool for up to two weeks after symptoms disappear.
- [22]
The U.K. Health Security Agency recommends getting checked for other sexually transmitted infections if you are diagnosed with Shigella.
- [23]
If you see a doctor for severe or persistent diarrhea, telling them about recent sexual contact can help them decide which tests you need and, if antibiotics are necessary, which ones are likely to work.
- [24]
The 510 extensively drug-resistant samples are about 3 percent of the nearly 17,000 collected since 2011.
Sources
1 independent publisher whose own reporting we read for this story.
- discovermagazine.comA Diarrhea-Causing Bacterium Spread Through Sex is Resisting Five Common Antibiotics
1 article · October 9, 2026
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