LANSING, MICHIGAN
It starts with something that looked perfectly healthy. A bowl of berries. Cilantro on a taco. Salad greens with a squeeze of lime. Nothing tastes wrong. Nothing smells off. Then, between two days and two weeks later, the body revolts — violently.
Health officials call it cyclosporiasis. In the hardest-hit counties, people use a blunter term: the "explosive diarrhea" parasite. Right now, it's tearing through Michigan at a pace that has investigators alarmed.
As of this week, the Michigan Department of Health and Human Services has confirmed over 300 cases — staggering for a state that typically records only about 50 in an entire year. The outbreak grew from scattered reports to more than 300 confirmed illnesses in roughly eleven days.
What's attacking these people?
The culprit is Cyclospora cayetanensis, a single-celled parasite invisible to the naked eye. Not a bacterium like Salmonella. Not a virus like norovirus. It's a protozoan that gets into the human gut and multiplies.
It spreads through the fecal-oral route — food or water contaminated with human waste somewhere in the supply chain. Crucially, you can't catch it directly from another person. The parasite needs days to weeks outside the body to become infectious. Each new case points back to a common contaminated source, usually food.
Here's the maddening twist: by the time victims are doubled over and case counts are climbing, the tainted food is often long gone — eaten, composted, or thrown out weeks earlier. Investigators are chasing a ghost.
The symptoms that empty a person out
Cyclosporiasis is rarely a killer in healthy adults, but anyone who's endured it will tell you it's a genuine ordeal. Symptoms appear 2 to 14 days after ingestion. The hallmark is frequent, watery diarrhea — sudden, repeated, hence the nickname.
Alongside it: loss of appetite, weight loss, stomach cramps, bloating, nausea, and low-grade fever. What sets this apart from a run-of-the-mill stomach bug is its stubbornness. Left untreated, it can drag on for weeks — sometimes over a month — with a cruel habit of seeming to fade before roaring back.
The fatigue can be profound. When your gut is inflamed for weeks and you can't keep food or fluids in, your body pays the price. Dehydration and weight loss are the real dangers, especially for the very young, the elderly, and the frail.
Who doctors worry about most
For most healthy people, cyclosporiasis is a miserable, drawn-out inconvenience. For others, it's serious.
"Though in most cases this illness causes discomfort from cramping, bloating and watery diarrhea, we are concerned about individuals who may be immunocompromised due to cancer treatment or an organ transplant as the effects may be more severe," said Lynn Sutfin of the Michigan Department of Health and Human Services.
A person on chemotherapy, someone living with HIV, a recent transplant recipient — for them, an infection that flattens a healthy adult can spiral into prolonged, dangerous illness. And because cyclosporiasis can masquerade as ordinary food poisoning, the most vulnerable patients may not get the specific testing they need until the parasite has dug in for days or weeks.
The manhunt for the poisoned food
The MDHHS, together with the Michigan Department of Agriculture and Rural Development, is racing to trace the source. Confirmed cases cluster in southeast Michigan counties: Monroe, Lenawee, Washtenaw, Wayne, Shiawassee, Jackson, and Livingston.
But as of July 4, no specific grower, supplier, or product has been publicly identified — and no recall issued. That absence reflects just how difficult these investigations are.
History offers a rogues' gallery of suspects. Past cyclosporiasis outbreaks have been traced to imported fresh produce eaten raw: raspberries, basil, snow peas, mesclun lettuce, cilantro. Produce that's delicate, often imported, eaten uncooked, and nearly impossible to fully sanitize once contaminated. You can't scrub a microscopic parasite off a lettuce leaf, and a quick rinse under the tap is no guarantee.
Not just a Michigan problem
While Michigan is the epicenter, the parasite hasn't respected state lines. Federal authorities have tracked cases across roughly 17 states this season, including Pennsylvania and New Jersey, with at least 20 hospitalizations nationwide. Cyclospora has a seasonal rhythm — cases climb in late spring and summer — and 2026 is shaping up to be punishing.
The national picture complicates the hunt. If contaminated produce entered the supply chain through a distributor shipping across multiple states, Michigan may be one visible piece of a much larger problem. Investigators must interview hundreds of sick people, asking each to recall what they ate weeks ago, to find the single ingredient they all share. Painstaking, imperfect detective work.
Why this keeps happening
Public-health specialists have warned for years that America's appetite for fresh, year-round produce carries risk. Much of the delicate produce eaten in the U.S. during certain months is imported from regions where irrigation or washing water may be contaminated. Cyclospora is endemic in many tropical and subtropical areas, and it doesn't take much — a single contaminated water source at a single farm — to seed an outbreak thousands of miles away.
Unlike bacteria, Cyclospora can't be knocked out by standard chemical washes, refrigeration, or freezing. Cooking kills it, but the whole appeal of a raspberry or cilantro is eating it raw. That's why these outbreaks recur summer after summer.
The good news: cyclosporiasis is treatable. The standard therapy is a course of the oral antibiotic trimethoprim-sulfamethoxazole (Bactrim, Septra, Cotrim) taken for about 10 days. The problem is getting to that diagnosis — routine stool tests don't always look for this parasite unless a doctor specifically asks.
What this means for you
If you live in Michigan or a neighboring state and develop watery diarrhea that won't quit — especially lasting more than a few days, fading and returning — contact a healthcare provider and mention the cyclosporiasis outbreak. That prompt can be the difference between targeted testing and being sent home with generic advice while the parasite settles in.
Stay hydrated. The single greatest danger is fluid loss. Watch for signs of dehydration: dizziness, racing heart, dramatically reduced urination, extreme fatigue.
Take extra care if you or someone in your household is immunocompromised. For them, cyclosporiasis warrants a lower threshold for calling a doctor.
And while investigators haven't named a culprit food yet, the sensible precaution is the same: wash all fresh produce thoroughly under running water; understand that washing reduces but doesn't eliminate risk; and remember that cooking is the only method that reliably destroys the parasite.
The bottom line
An outbreak that's grown from a trickle to more than 300 confirmed cases in less than two weeks is not routine. It's a fast-moving, still-unsolved public-health puzzle, and the fact that officials can't yet name the food means the source may still be out there. Until the disease detectives close the case, the smartest move is simple vigilance — knowing the symptoms, hydrating hard, washing what you eat, and speaking up quickly if your gut suddenly turns against you.
Case counts and source information are changing rapidly. Anyone who is sick or worried should rely on their local health department and a medical provider for the most current, personalized guidance.
