Parasite Outbreak Spreads Across 43 Ohio Counties With Nearly 200 Sickened

A Fast-Moving Outbreak With a Tricky Parasite

Ohio has confirmed 177 cases of cyclosporiasis in 2026 — 171 of which appeared in less than two weeks, mostly since June 20, across 43 of the state's 88 counties. The culprit is the parasite Cyclospora cayetanensis, which is typically spread by eating contaminated fruits and vegetables. What makes this outbreak especially alarming isn't just the speed at which it spread — it's how easily it can be missed.

Twenty-eight Ohioans have been hospitalized, and while cyclosporiasis is not typically life-threatening, it can cause watery, and sometimes explosive, diarrhea. Ohio Department of Health Director Dr. Bruce Vanderhoff said there have been no deaths, but stressed: "This is a serious illness that can cause dehydration and require people to seek emergency medical care, and it should be taken seriously."

Ohio Is Not Alone — This Is a Regional Crisis

Ohio's numbers are troubling, but they're just part of a larger picture. Cases of the fast-moving parasitic illness linked to contaminated produce have numbered over 1,400 in Michigan and Ohio combined, putting public health officials on alert as investigators have yet to identify the source of the outbreak. Michigan typically sees about 50 cases per year, meaning cases there are currently about 13.5 times higher than average.

Nationally, the infection has been reported in Michigan, Ohio, Illinois, Indiana, New York, North Carolina, Texas, and other states. The CDC has found at least 17 states reported cyclosporiasis cases between early May and mid-June. Yet the CDC is not keeping up with national data on recent outbreaks — the agency last posted an update on July 1, which lists only 145 cases nationwide through June 16. That figure dramatically understates what's actually happening on the ground.

The Source Is Still Unknown — and That's a Problem

No common source has been identified, and investigators are still searching for the origin of the outbreak. One local official believes the sheer volume of cases is pointing in a direction. Lorain County Epidemiology Supervisor Mitch Dandurand noted that "just the sheer number of cases both locally and statewide indicates it's a commonly consumed produce item such as lettuce." Past foodborne outbreaks of cyclosporiasis have been linked to various types of imported fresh produce, such as raspberries, basil, snow peas, mesclun lettuce, and cilantro.

Making matters worse, the parasite is notoriously hard to catch in routine testing. Cyclosporiasis is frequently misdiagnosed — not because physicians lack clinical knowledge, but because the parasite does not appear on standard commercial stool panels. Patients may receive multiple rounds of antibiotics that do nothing, visit urgent care repeatedly without resolution, or simply endure weeks of symptoms while the infection is attributed to food poisoning, IBS, or viral gastroenteritis. Doctors must specifically order the right test — it won't show up otherwise.

What Ohioans Should Know Right Now

Symptoms typically begin 7 to 14 days after ingesting contaminated food or water — meaning the exposure may feel entirely disconnected from when illness begins. A distinctive clinical feature is that cyclosporiasis is often relapsing — symptoms may appear to resolve and then return, sometimes repeatedly, without treatment. This cycle-within-illness pattern gives the parasite its name and is one of the key diagnostic clues.

Cyclosporiasis can be treated with antibiotics, and getting rest and plenty of fluids is also important to recovery. People should wash their hands with soap and water before and after preparing raw fruits and vegetables, and fruits and vegetables should be washed thoroughly under running water. If you've had prolonged or recurring diarrhea in recent weeks, it's important to see a healthcare provider and specifically mention cyclosporiasis, and ask for stool testing, because not all stool testing routinely includes it. With investigators still racing to pinpoint the source, that advice could make all the difference.