Health officials say contaminated produce is the leading theory, but no specific food item, supplier or grower has been identified.
LANSING, Mich. — Michigan health officials are investigating a fast-growing cyclosporiasis outbreak that has sickened more than 700 people and led to 36 reported hospitalizations, with the source still unknown as cases spread across the state.
The outbreak marks a sharp break from Michigan’s normal pattern for the intestinal illness, which is caused by the microscopic Cyclospora parasite. State officials said Michigan usually identifies about 50 cases in a full year, but reports climbed from more than 170 cases on June 30 to more than 700 by July 6. The Michigan Department of Health and Human Services said contaminated fresh produce is the leading theory, though investigators had not named a specific food, supplier or grower.
State officials first announced the outbreak July 1 after more than 170 cases were reported in Monroe, Lenawee, Washtenaw, Wayne, Livingston, Shiawassee and Jackson counties over nine days. The count kept rising through the holiday weekend. By Monday night, July 6, State Chief Medical Executive Dr. Natasha Bagdasarian said Michigan had confirmed 708 cases, up from 681 earlier the same day. “Based on the unusual number of cases we have identified in a little over a week, we anticipate additional cases of illness being reported,” Bagdasarian said when the outbreak was first announced.
Cyclosporiasis infects the small intestine and can cause watery diarrhea, frequent and sometimes explosive bowel movements, stomach cramps, bloating, nausea, fatigue, loss of appetite and weight loss. Symptoms can begin two to 14 days after exposure and can last from several days to more than a month if untreated. Health officials said symptoms can also return after seeming to improve. The illness is diagnosed through stool testing. No deaths had been reported in the federal case count released before Michigan’s latest surge, but hospitalizations tied to the Michigan outbreak had reached 36 by July 6.
The highest case counts remained in Monroe, Lenawee, Washtenaw, Wayne, Shiawassee, Jackson, Oakland and Livingston counties, according to state health officials. Monroe County has been one of the main hot spots, with local officials reporting a large share of the state’s confirmed infections. The outbreak also comes as federal officials track cyclosporiasis cases across the country. The Centers for Disease Control and Prevention reported 145 domestically acquired cases in 17 states among people who became sick from May 1 through June 16, before the full Michigan increase was reflected in public counts.
Investigators are looking at food histories and other records to find whether the Michigan illnesses share a common source. Cyclospora is usually spread when people eat or drink something contaminated with feces carrying the parasite. Past outbreaks have been linked to fresh produce, including leafy greens, herbs and berries. Officials have not said whether the Michigan outbreak is tied to one product, several products or separate exposure points. They also have not announced a recall tied to the outbreak. The lack of a named source has left the investigation centered on interviews, lab testing and tracing possible food supply links.
Ohio has also reported a rise in cyclosporiasis cases, with state health officials there confirming 177 cases as of July 2. Most of those Ohio cases were reported after June 20 and were spread across 43 counties. Federal officials said the true number of infections is likely higher than reported because some people recover without medical care and others may not be tested for Cyclospora. The illness is nationally notifiable, which means confirmed cases are reported to public health agencies so investigators can track patterns and detect outbreaks tied to a shared source.
Michigan officials said the response includes the state health department, the Michigan Department of Agriculture and Rural Development and local health departments. Their work includes collecting patient interviews, reviewing possible food exposures and coordinating with federal partners as needed. Health officials said food businesses and commercial kitchens should take extra care with raw produce during the investigation. Officials also said cooking food can kill the parasite, but the outbreak investigation has not yet narrowed the risk to one produce type or one point in the supply chain.
For patients, the outbreak has meant days or weeks of severe gastrointestinal illness. Some cases can be treated with antibiotics, but untreated infections may linger or relapse. Public health officials said people with sudden and ongoing diarrhea should contact a health care provider and their local health department. That statement was framed as part of the investigation because confirmed patients can help officials identify common meals, stores, restaurants or ingredients. Bagdasarian said outbreaks have been occurring across the United States and that Michigan’s rapid increase showed the state was facing an unusual cluster.
The next step is finding the source. State and local investigators are expected to keep reviewing food histories and laboratory data while more cases are reported. As of Wednesday, July 8, no specific contaminated item had been identified, no public recall had been announced and Michigan remained the center of the largest known spike.
Author note: Last updated July 8, 2026.