Michigan health officials are investigating a rapidly growing outbreak of Cyclospora, a parasite that causes severe gastrointestinal illness, after reported cases statewide jumped to more than 700.
That’s more than four times as many as last week.
The surge marks one of the largest cyclosporiasis outbreaks ever recorded in the state, far exceeding the roughly 50 cases Michigan sees in a typical year.
The Michigan Department of Health and Human Services (MDHHS) confirmed the latest case count and said 36 people have been hospitalized in connection to the outbreak.
Mid‑Michigan among hard‑hit regions
While the largest increases are occurring in Southeast Michigan, mid‑Michigan counties are also reporting dozens of cases.
Below is the most recent county-level breakdown, which is pulled weekly based on the current caseload.
Spokesperson Lynn Sutfin says that these numbers are constantly fluctuating and should not be interpreted as real-time case numbers.
Clinton, Macomb, Lapeer and Hillsdale each have 4.
Allegan, Montcalm and Ottowa each have 2.
Calhoun, Charlevoix, Gladwin, Kent, Midland, Houghton, Leelanau and Manistee all have 1.
Jackson County Deputy Health Officer Matthew Budd said investigators are conducting detailed interviews with every person who tests positive to identify what they ate in the days before symptoms began.
“Just to give people an idea of what goes into this surveillance: we get a laboratory result confirming the organism and we reach out to every individual that tests positive,” Budd said. “We go through a food history of the last week or more with these people.”
What Cyclospora is — and why testing matters
Cyclospora cayetanensis is a microscopic parasite spread through food or water contaminated with feces. It is not known to spread directly from person to person.
Symptoms for Cyclosporiasis, the illness cause by infection with the Cyclospora parasite, occur two to 14 days after exposure and may include:
- Watery diarrhea (most common)
- Loss of appetite
- Weight loss
- Cramping
- Bloating
- Increased gas
- Nausea
- Fatigue
Less common symptoms may include:
- Vomiting
- Body aches
- Headache
- Low-grade fever
- Other flu-like symptoms
Without treatment, Cyclospora symptoms can linger for weeks. Illness may ease and then flare up again — diarrhea can stop and return, and fatigue often sticks around even after the stomach issues have passed.
Budd says people with diarrhea lasting more than a few days should contact a medical provider and ask about testing.
“That testing is really critical,” Budd said. “If that diarrhea lasts more than a few days, talk to your provider and actually get tested.”
Budd emphasized that testing is essential because the illness resembles other foodborne infections.
“There’s not really any other symptoms that are going to help distinguish this illness,” he said.
Diagnosing the parasite can also be unpredictable. Even when people are sick, they don’t always shed enough of the parasite in their stool for labs to detect it.
That means a single test can come back negative even if someone is infected. Because Cyclospora can show up in the stool only occasionally — and sometimes in very small amounts — health providers often need several samples collected on different days to confirm the illness.
No identified source yet
Health departments are now trying to figure out where the parasite entered the food supply.
Investigators are reviewing detailed food histories from people who test positive, which Budd says is a contributing factor in the time it’s taking to identify the source of the outbreak.
“You know, if you start to think back a day or two days or three days ago of what you ate for every meal and every snack, and if you ate a burger: what produce was on the burger, did you have any condiments on the burger, what was on the side? All of these questions have to be asked,” Budd said. “We're looking at over 600 people in the state of Michigan. We're trying to narrow it down still.”
Despite hundreds of interviews, investigators have not identified a specific food item, grower or supplier linked to the outbreak.
Previous U.S. outbreaks have been tied to fresh produce such as bagged salad mixes, cilantro, basil, raspberries, snow peas and green onions – but MDHHS says no such link has been found in Michigan so far.
Health officials provide safety precautions
No one fully knows how Cyclospora contaminates food or water, but health officials have done extensive research into preventing Cyclosporiasis.
While the investigation continues, state and local health departments are urging residents to take additional precautions when handling fresh produce. Recommendations from the Michigan Department of Agriculture and Rural Development (MDARD) include:
- Wash all fruits and vegetables thoroughly under running water before eating, cutting or cooking.
- Scrub firm fruits and vegetables, such as melons and cucumbers, with a clean produce brush.
- Cut away any damaged or bruised areas on fruits and vegetables before preparing and eating.
- Refrigerate cut, peeled or cooked fruits and vegetables as soon as possible.
In a partnership with MDARD, Michigan’s Department of Health released a statement with additional recommendations to prevent spread:
- Cook when you can. Heating food to 158°F (70°C) or higher kills Cyclospora.
- Wash hands with soap and water before and after handling or preparing food.
- Wash and sanitize utensils and surfaces before and after handling food. Wash and sanitize display cases and refrigerators where fresh produce is stored.
- Wash and sanitize cutting boards, surfaces and utensils used to prepare, serve or store fresh produce.
The CDC also monitors foodborne outbreaks with updates available online.
When to seek care
MDHHS urges people who develop sudden or ongoing diarrhea lasting more than a few days to contact a healthcare provider and notify their local health department.
The CDC recommends treatment with antibiotics along with rest and plenty of fluids to prevent dehydration – and notes that symptoms can last weeks without it.