A parasitic infection called Cyclosporiasis known for causing weeks of watery, sometimes explosive diarrhea has spread across 31 states, with Michigan reporting more cases than anywhere else in the country and investigators still unable to pin down where it started.
A growing and unusually stubborn outbreak
Michigan has recorded more than 1,000 Cyclosporiasis cases within a two week span, making it the largest outbreak in the state’s history and one of the biggest seen nationally in years. New York has reported close to 300 cases, while Ohio and Illinois have each logged well over 100. Nationally, the Centers for Disease Control and Prevention has confirmed more than 840 cases as of July 9, with another 1,500 suspected illnesses still under review. At least 86 people have been hospitalized, though no deaths have been reported. What has caught investigators off guard is the sheer scale of this year’s outbreak paired with the total absence, so far, of a single identifiable source.
A parasite that hides in produce and water
Cyclosporiasis is caused by a microscopic parasite called Cyclospora cayetanensis, typically spread through fresh produce or water contaminated with fecal matter. Unlike many foodborne illnesses, it does not usually pass directly from person to person, which means each case likely traces back to something someone ate or drank. Cyclosporiasis symptoms can include frequent and sometimes explosive diarrhea, cramping, bloating, fatigue, nausea and a low grade fever, and without treatment the illness can drag on for weeks or even more than a month, occasionally letting up briefly before returning.
Restaurants respond in different ways
With no confirmed source, some restaurants have decided not to wait for answers. A pizzeria in Stevensville, Michigan, pulled lettuce, tomatoes and onions from its menu entirely, saying it would rather pause serving those items than take an unnecessary risk. A restaurant in Idabel, Oklahoma, began soaking and rewashing produce a second time, even items that arrive pre washed, and removed kale and parsley because they are harder to clean thoroughly. Another Michigan restaurant clarified that it has never used bagged lettuce, opting instead to cut whole heads in house daily, a practice it says predates the outbreak and was adopted for freshness rather than safety concerns.
Major chains stay quiet
Despite the scale of the outbreak, most large fast food chains have said little publicly. Requests for comment sent to several major companies and the industry’s national trade association went largely unanswered. One major chain did respond, saying it is monitoring the situation closely and does not currently believe its sourced ingredients are connected to the Cyclosporiasis outbreak, while adding that guest and employee safety remains its top priority.
Experts say caution is warranted while answers are pending
Food safety specialists say the uncertainty itself is part of what makes this Cyclosporiasis outbreak notable. A microbiologist who studies the parasite has suggested people limit fresh fruit and salad bar items when eating out, since diners typically have no way to know how thoroughly produce was washed or where it originated. He noted that Cyclosporiasis resists standard chlorine based cleaning and that rinsing alone may not remove it if the parasite is lodged in the crevices of leafy greens or berries. An infectious disease physician added that the inability to trace this outbreak back to a specific farm or supplier, something investigators are usually able to do, suggests there may be multiple contaminated sources or several unrelated outbreaks happening at once. A food safety attorney who has represented people sickened by the illness in the past described it as unpleasant and often long lasting, urging both home cooks and diners to be more careful than usual.
What comes next
Health officials continue to investigate the Cyclosporiasis outbreak’s origin, and case counts are expected to keep climbing as suspected illnesses are confirmed. In the meantime, basic precautions such as thoroughly washing produce, cooking fruits and vegetables when possible, and staying alert to restaurant sourcing practices remain the most practical tools available while a definitive source remains unidentified.
If you are experiencing persistent digestive symptoms, it’s worth checking in with a healthcare provider rather than waiting for them to resolve on their own.
