Brian Reed: Hey. Good to be here.
Eliza Ward: Yeah, likewise. You've got something.
Brian Reed: Science Alert published a piece — October 2026 — and I've been sitting with one number from it. UCLA is seeing roughly one extensively drug-resistant Shigella case a month right now.
Brian Reed: One. For the entire year of 2022.
Eliza Ward: Wait — Shigella. As in the gut bug. Food poisoning, contaminated water. That one.
Brian Reed: That's the thing. Shangxin Yang — molecular biologist at UCLA — called it, and I'm going to quote this directly, 'almost like an explosion of this pathogen in the community.' And what she's describing isn't just a food-safety story anymore.
Eliza Ward: Right. Because it's transmitting sexually now. That's — yeah. That's actually the part that changes everything about who we're talking to when we say 'wash your hands.'
Brian Reed: And that's actually — let me try to say this plainly, because I think the headline buries it. Shigella is basically a stomach bug you'd get from a bad taco. It lives in the gut. The new part is that sexual contact, specifically oral-anal contact, can move it person to person the exact same way contaminated food used to. And the strains spreading that way happen to be the ones antibiotics can't touch.
Eliza Ward: That's the click. The bug didn't change — the route did.
Brian Reed: Right. And the CDC has been tracking this nationally. XDR isolates went from zero percent — literally zero — during 2011 to 2015, to 8.5% by 2023. That's not noise.
Eliza Ward: That number's real, but it's also three years old now. 2023 is the most recent CDC surveillance figure we have. We're in late 2026. So whether 8.5% held or — wait, whether it climbed further, we actually don't know.
Brian Reed: And the CDC identifies MSM — gay, bisexual, men who have sex with men — as the group more likely to acquire the resistant strains through sexual transmission. Which is who we're talking about at UCLA.
Eliza Ward: This isn't even new globally. The UK had a sexually transmitted XDR Shigella sonnei outbreak, first detected September 2021, documented in The Lancet Infectious Diseases. Among MSM. Years before this Science Alert piece.
Brian Reed: Wait — The Lancet published that in 2022?
Eliza Ward: 2022. Peer-reviewed, international precedent, same population, same resistance profile. And I'm — I mean, I don't see evidence that American public health was visibly watching.
Brian Reed: So the pace is what's actually new. The mechanism, the population, the resistance arc — that was documented. What UCLA is showing us is that the acceleration is now happening here, and it's fast enough that Shangxin Yang is reaching for the word explosion.
Eliza Ward: But that framing — 'explosion of one pathogen' — that's actually where I think the coverage is going to get this wrong.
Brian Reed: What do you mean, wrong?
Eliza Ward: People are going to picture one super-bug strain. One rogue clone spreading through a network. And if that's your mental model, you think containment means trace it, isolate it, stop it. But that's not what the experts are describing.
Brian Reed: No — the quote from Science Alert is specifically 'multiple overlapping variants emerging that are all quickly becoming resistant to the drugs we use to treat them.' That's not one clone. That's — I mean, that's a different problem entirely.
Eliza Ward: Right. And does that actually change anything on the ground? Clinically?
Brian Reed: It changes everything. Because if it's one strain, you can maybe sequence it, track it, watch it. If it's multiple overlapping variants — azithromycin doesn't work, ciprofloxacin doesn't work, trimethoprim-sulfamethoxazole doesn't work — you're not hunting one thing. The whole drug shelf is just... emptying.
Eliza Ward: Sarath Nath at Stony Brook Medicine put it carefully — most cases still resolve without antibiotics. But the fraction that don't? They're landing in beds.
Brian Reed: CDC data. Over one-third of XDR patients hospitalized. And nearly half of those with known HIV status were HIV-positive. So picture — actually, let me make it concrete. Man in his thirties. Develops cramping, diarrhea, four days after sex. Thinks it's a stomach bug. Day four, 102-degree fever. He's in urgent care. Clinician reaches for azithromycin. Doesn't work. Tries cipro. Also resistant. That's not hypothetical — that's exactly what this data describes.
Eliza Ward: And the clinician has no flag that says 'this is a sexually acquired strain, treat it differently.' The Science Alert piece has an expert saying it's highly likely that if you contracted Shigella through sex, you need different treatment than someone who got it from travel. That's not in most urgent care workflows.
Brian Reed: And there's a layer under this we haven't gotten to yet — what doxyPEP might be doing to resistance dynamics in the same population. That part gets complicated fast.
Eliza Ward: That's the piece I keep wanting to separate out — because doxyPEP is doing something real and good. Syphilis prevention, chlamydia prevention, MSM populations who were getting hammered by bacterial STIs. That's confirmed. But then there's a 2024 modeling study in The Lancet Microbe — and this is where I want to be careful about what it actually says — it found doxyPEP substantially reduces gonorrhea prevalence in MSM but accelerates resistance timelines for Neisseria gonorrhoeae. Those two things are true at the same time.
Brian Reed: Hang on — accelerates resistance timelines. Meaning the drug that's preventing the infection is also speeding up the clock on that infection becoming untreatable.
Eliza Ward: For gonorrhea, yes. That's what the modeling shows. Now — does that extend to Shigella circulating in the same population? I don't know. And I want to be clear: that's inference, not data. The mechanism is plausible — you're running a tetracycline through a concentrated population, you're selecting for resistance — but there's no study I'm aware of that traces the XDR Shigella strains back to doxyPEP uptake specifically.
Brian Reed: So it could just be two things happening in the same community at the same time.
Eliza Ward: Right — correlation, not causation. And the surveillance gap makes this worse. The CDC's most recent XDR prevalence figure nationally is 8.5%, from 2023. We are in late 2026. Three years of national data are just... missing. So we're trying to reason about a doxyPEP-resistance link using a Shigella baseline that's already stale.
Brian Reed: That's — yeah. That's the actual hole in the story.
Eliza Ward: Picture a researcher right now trying to model this. She's got the UCLA site data — one case a month — which is a single hospital, not a national number. She's got an 8.5% CDC figure that's three years old. She's got a Lancet Microbe model built for Neisseria gonorrhoeae, a completely different organism. And she's supposed to tell a clinician whether the doxyPEP her patient started in July is contributing to the Shigella resistance problem by September. The WHO has flagged AMR as a critical global threat but that designation doesn't fill the data gap.
Brian Reed: So the concrete thing to watch — is there a sequencing study in the pipeline? Something that actually traces these XDR variants genetically back to the communities with highest doxyPEP uptake?
Eliza Ward: That's the thing to watch. If that study exists and shows the link — that changes the doxyPEP calculus completely. If it doesn't, we're still flying blind on whether the prevention tool and the resistance surge are cause and effect or just neighbors.
Brian Reed: And that's — I mean, that's the core issue. The prevention tool and the resistance problem are operating in the same community at the same time, and the sources don't give us a clear path out of that. Like, no new drug class is identified anywhere in what we've read as a ready replacement for the agents that are failing against XDR Shigella. Azithromycin's gone, cipro's gone, trimethoprim-sulfa's gone. What's actually next in line?
Eliza Ward: Nothing's waiting. That's — wait, that's Sarath Nath's whole point. He says most shigellosis resolves on its own, which is true, but the growing fraction that doesn't? There's no replacement drug class identified. You're not managing the outbreak toward a new treatment. You're just watching the treatment options narrow.
Brian Reed: So the actual open question — do you continue doxyPEP, accept that AMR costs are part of the tradeoff, and just... live with a growing hospitalization rate in a population that's already managing HIV? Or does that tradeoff eventually force someone to rethink the whole prophylaxis strategy? And if so — what replaces it? Because I genuinely don't know, and I'm not sure the sources do either.
Eliza Ward: Neither do I. That's the honest answer. The episode ends there.
