Michigan health officials are scrambling to identify the source of an unprecedented outbreak of the foodborne parasite Cyclosporiasis, which has already infected more than 1,200 people across the state in just over two weeks, sending dozens of patients to hospitals with severe dehydration.

Since the state’s first confirmed case was reported on June 22, the Michigan Department of Health and Human Services (MDHHS) has recorded approximately 1,250 confirmed infections as of Thursday morning, July 9. About 40 patients have required hospitalization because of severe dehydration caused by the illness.

The rapid spread has alarmed public health officials. Michigan typically reports only about 50 Cyclosporiasis infections annually, making this year’s outbreak one of the largest ever recorded in the state.

Authorities have yet to identify the source of the outbreak, although investigators believe contaminated fresh produce is the most likely cause.

Cyclosporiasis infections occur when people consume food or water contaminated with the microscopic parasite.

Symptoms usually appear about one week after exposure but can develop anytime between two and 14 days after eating contaminated food. Patients commonly experience severe watery diarrhea, frequent bowel movements, loss of appetite, fatigue and mild fever. Symptoms may last two weeks or longer and can recur if the infection is not properly treated.

Health officials advise anyone experiencing symptoms to stay hydrated by drinking electrolyte-rich fluids and to seek immediate medical attention if diarrhea becomes severe or is accompanied by fever.

Search for the source continues

The MDHHS, working alongside local health departments, the Michigan Department of Agriculture and Rural Development (MDARD) and the Centers for Disease Control and Prevention (CDC), has launched a large-scale investigation involving hundreds of patient interviews and detailed reviews of grocery purchases, restaurant visits and food distribution chains.

Most Michigan cases have been concentrated in southeast Michigan, particularly in Wayne, Oakland, Washtenaw, Macomb, Livingston, Monroe, Lenawee, Jackson and Shiawassee Counties.

Although dozens of infections have been reported in Wayne County, including communities surrounding Dearborn, officials have not identified any single restaurant, grocery store or food supplier linked to the outbreak.

The outbreak also extends beyond Michigan. Neighboring Lucas County, Ohio, has reported more than 300 cases, while northwestern Ohio has surpassed 500 infections.

Michigan’s chief medical executive, Dr. Natasha Bagdasarian, said evidence strongly suggests a common source outbreak, although investigators have not yet identified the specific product responsible.

No food recalls have been issued, and authorities have not identified a farm, distributor or importer connected to the illnesses.

That uncertainty makes it difficult to determine whether contaminated products remain in circulation.

Bagdasarian said investigators currently suspect fresh agricultural products because previous Cyclospora outbreaks have been linked to raspberries, lettuce, cilantro, basil, peas and green onions.

She advised consumers to consider frozen raspberries because the fresh fruit can be difficult to wash thoroughly due to its delicate surface.

She also recommended purchasing whole heads of lettuce rather than pre-washed bagged lettuce, removing the outer leaves and washing the remaining leaves carefully.

For vegetables and herbs that can be cooked, including cilantro, basil and green onions, she recommended cooking them whenever possible to reduce the risk of infection.

The CDC has reported hundreds of additional Cyclosporiasis infections in 27 other states, suggesting the outbreak may involve a widely distributed food product.

Doctors urge caution, not panic

Dr. Hassan Dakroub, an infectious disease specialist with Corewell Health, said the outbreak represents more than a routine seasonal increase.

He said Cyclosporiasis outbreaks often point to widespread contamination somewhere within the fresh produce supply chain and noted that reported infections have steadily increased nationwide since the late 1990s.

Some public health experts now consider the parasite endemic in parts of the developing world.

Dr. Mazen Elatrache, a gastroenterologist and advanced endoscopy specialist at Henry Ford Health, said several factors may be contributing to Michigan’s unusually high case count.

Those include contaminated fruits and vegetables, increased consumption of fresh produce during the summer months, flooding or heavy rainfall that contaminates irrigation water with sewage, and increased travel that facilitates the spread of foodborne illnesses across state lines.

Both physicians agreed that what distinguishes the current outbreak is not only the number of cases but also the complexity of the investigation.

Tracing the parasite is difficult

Dakroub explained that Cyclosporiasis outbreaks are among the most difficult foodborne illnesses to investigate because symptoms often do not appear until two days to two weeks after exposure.

During that time, patients may have eaten dozens of meals, shopped at multiple stores and visited numerous restaurants, making it extremely difficult to identify the contaminated food that caused the illness.

Fresh fruits and vegetables associated with the parasite are also highly perishable and are often consumed or discarded before investigators begin interviewing patients.

As a result, health officials conduct detailed epidemiological investigations with every patient, reviewing everything they consumed during the two weeks before symptoms began and comparing responses across hundreds of cases.

If investigators identify one food item repeatedly appearing among patients, they begin tracing its distribution from retailers to wholesalers, farms and, ultimately, its country of origin.

Dakroub said that process can take weeks or even months, especially when products move through complex domestic and international supply chains before reaching consumers.

He also believes climate change may be contributing to the growing frequency of Cyclosporiasis outbreaks by increasing flooding and affecting irrigation water quality, while globalization has expanded the movement of fresh produce across international borders, making contamination events more difficult to detect and contain.

Elatrache emphasized that the current outbreak should be taken seriously but cautioned against unnecessary alarm.

“We cannot say the situation is fully under control until the source of contamination has been identified,” he said.