What travelers need to know about 'explosive diarrhea' outbreak that's sparked health alarm across US
Health officials in the US have issued a warning after a fast-spreading outbreak of "explosive diarrhoea" left dozens of people seriously ill, with cases now confirmed across 17 states.
The Center for Disease Control and Prevention (CDC), alongside the Food and Drug Administration (FDA), confirmed the outbreak has been linked to cyclosporiasis, an intestinal illness caused by a microscopic parasite called Cyclospora cayetanensis.
It's typically contracted by eating contaminated fresh produce or drinking unclean water.
As of late June 2026, 145 laboratory-confirmed cases had been officially recorded, though that figure is likely to be a significant undercount, with Michigan alone reportedly logging around 1,000 diagnoses in just two weeks. Of those tracked nationally, at least 20 people have needed hospital treatment, though no deaths have been reported.
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What's particularly concerning investigators is that none of the infected patients had travelled internationally in the fortnight before falling ill, confirming the parasite was picked up domestically through a food or water source that's still being traced.
If you're planning a trip to the US anytime soon, whether that's for the final stretch of the World Cup or otherwise, it's worth knowing exactly what you're dealing with.
What is cyclosporiasis and how do you catch it?
Cyclosporiasis isn't native to the UK, but can be picked up in countries across the world, including the US, Central and South America, South and Southeast Asia, the Middle East and Africa. It tends to spike during spring and summer months.
The illness is typically caught by eating contaminated fresh produce, such as salad, herbs or berries, or by drinking unclean water. Historical outbreaks have previously been linked to items including basil, cilantro, mesclun lettuce mixes, raspberries, and snow peas or sugar snap peas.
Unlike bacterial infections such as E. coli or Salmonella, Cyclospora only uses humans as a host, meaning contamination typically occurs when infected agricultural workers lack proper hygiene facilities, or when sewage-contaminated water is used to irrigate crops.
Importantly, the infection cannot be passed directly from person to person, so catching it from a friend or family member who's already infected isn't possible.
Health officials have also warned that washing your fruit and vegetables at home may not be enough to protect you. The parasite is resistant to standard sanitising chemicals, including chlorine washes used by commercial food processors, and its sticky outer shell clings tightly to the rough surfaces of leafy greens and berries.
What are the symptoms of cyclosporiasis?
Symptoms usually appear somewhere between two days and three weeks after infection, which is part of what makes tracing the source of outbreaks so difficult.
The most commonly reported symptoms include:
Loud, watery or explosive diarrhoea, loss of appetite, bloating, burping and farting, extreme tiredness, a low-grade fever, stomach cramps, nausea, and vomiting.
If left untreated, symptoms can last anywhere from a few days to over a month, and may repeatedly disappear and then relapse.
Because the parasite is difficult to detect, standard stool tests can miss it entirely, so health departments are urging anyone with prolonged symptoms to specifically request a Cyclospora PCR test from their doctor, which can then be treated with a targeted course of sulfa-based antibiotics.
Michigan's health department has recommended that restaurants and kitchens cook raspberries and leafy greens where possible, and remove the outer layers of lettuce and green onions before serving, as a precaution while the source of the current outbreak remains unidentified.
Thomas Bamford