Shigella is a bacterial gut infection. It spreads easily during sex, it's rising sharply in this community, and it's becoming resistant to the antibiotics that used to clear it quickly.
It's not technically classified as an STI. That distinction doesn't matter much here — it moves through sexual networks, it disproportionately hits gay and bisexual men, and the resistance picture means treating it wrong doesn't just delay your recovery, it makes the problem worse for everyone.
If you've got gut symptoms after sexual contact, or a partner just told you they've been diagnosed: this is the guide.
🔩 How It Spreads
Shigella is fecal-oral. A tiny amount of stool, invisible to the naked eye, is enough — the infectious dose can be as low as 10–100 bacteria. That's what makes it unusually easy to pick up during sex.
The routes:
- Rimming: the most efficient sexual transmission route. Direct oral-anal contact without a barrier.
- Fingers: hand-to-anus contact, then hand-to-mouth — directly or via touching a partner's mouth or food.
- Toys: oral contact with toys that have had anal contact without being covered or cleaned first.
- Hands: not washing properly after anal play before touching your own or a partner's face.
It doesn't transmit via blood or semen. Standard anal sex isn't a direct route. The transmission is in the handwashing — or lack of it — around sex.
⚠️ What It Does to You
Symptoms typically hit within 1–4 days of exposure.
The picture: diarrhoea (sometimes bloody), stomach cramps, fever, and nausea. It looks exactly like food poisoning. Most people assume that's what it is. If you've had unprotected rimming or oral-anal contact recently, that assumption isn't good enough.
Severity varies. Some people clear it in a week without treatment. Others — especially anyone who's immunocompromised — can get a prolonged or severe illness, particularly with a resistant strain. Don't wait it out if symptoms are significant.
🦠 The Resistance Problem
This is the part that changes what you should actually do.
In England in 2025: 86% of Shigella sonnei strains were resistant to first-line antibiotics. 94% of Shigella flexneri. That's not a marginal trend — ciprofloxacin, which used to be the standard treatment, is no longer reliably effective against the strains circulating in MSM sexual networks.
What this means in practice: don't self-treat with antibiotics you have at home. The wrong antibiotic against a resistant strain delays proper treatment and adds to the resistance problem. And a standard GP visit for gut symptoms may not automatically include sensitivity testing — you need to ask for it specifically.
What to say: "I want a stool culture with sensitivity testing. I know there's high antibiotic resistance in sexually transmitted Shigella in this community."
That prompt will get you the right test. Get the sensitivities before committing to a treatment. If you're prescribed something and don't improve within a couple of days, go back — this isn't a situation for waiting it out.
🔬 Getting Diagnosed
Ask for: a stool sample, culture, and sensitivity testing. Tell the clinic you've been symptomatic after sexual contact and want Shigella investigated with resistance testing included.
Most sexual health clinics that see MSM are now across this. If yours isn't, be direct about what you need.
While you're there: Get a full STI screen. The sexual contact that transmits Shigella can also transmit gonorrhoea, chlamydia, syphilis, and Hepatitis A. A Shigella diagnosis is a reason to check everything — not just the gut.
Hydration: Whatever else is happening, keep your fluids up. Oral rehydration salts (available at any pharmacy) are more effective than water alone. Get them early.
🛡️ While You're Ill: Stopping the Spread
No sex — particularly no rimming or any anal-oral contact — until you've been symptom-free for at least 48 hours. UK guidance recommends waiting 7 days after symptoms clear before resuming sexual activity.
Beyond sex:
- Wash hands thoroughly after every bathroom visit
- Don't prepare food for other people
- Don't share towels
- Avoid communal swimming pools until fully recovered
Shigella can be transmitted to household members and non-sexual contacts through normal hygiene lapses. The isolation isn't about stigma — it's about the infectious dose being genuinely tiny.
🔁 After Recovery
A few things worth knowing once you're clear:
You're not immune. A Shigella infection doesn't give you lasting protection. You can pick it up again from the same routes. The prevention steps — barriers for rimming, handwashing, not sharing toys — remain relevant.
Tell recent contacts. Shigella is transmissible before symptoms appear. Partners you were with in the days before you got ill may already be incubating it without knowing. A brief heads-up gives them the chance to get tested before it progresses, and to avoid passing it on further.
For resistant strains especially, that notification matters — the sooner someone gets the right treatment (based on sensitivities rather than a default prescription), the better their outcome.
The gut takes time. Even after the infection clears, some people experience gut sensitivity for a few weeks — irregular bowel habits, mild cramping. This usually resolves. If symptoms return or significantly worsen, go back to the clinic.
If you're on HIV treatment: Some antiretrovirals can interact with antibiotics used to treat Shigella. Make sure both your HIV clinic and the treating doctor know what you're taking.
🟢 Prevention Going Forward
No vaccine exists for Shigella — prevention comes down to barriers and hygiene.
- Dental dams or cut condoms for rimming: the direct fix for the highest-risk route. Available free from most sexual health clinics.
- Wash hands before and after anal contact, and before touching your own or a partner's face or mouth.
- Cover anal toys with condoms and replace the condom before any oral contact.
- Hepatitis A vaccination closes the other key fecal-oral risk during rimming — if you're not vaccinated, this is worth doing.
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