The cyclosporiasis outbreak causing explosive diarrhea and other digestive distress that started in May 2026 has now reached more than 3,000 cases in Michigan and Ohio. But because cyclospora infections are notoriously hard to track, health officials expect the real number to be even higher.
Besides tracking the growing number of cases, experts are also making their first suggestions about the source of the parasitic outbreak, pointing to lettuce or other salad greens. Since the investigation is still ongoing, officials also stress that other foods cannot yet be ruled out as the source. Current goals are to determine what type of produce is carrying the parasite and whether there is a common supplier that the outbreak can be traced back to.
According to experts, Cyclospora's distinct biological characteristics, delayed symptom development, and patients' hesitation make the outbreak especially challenging to investigate, while recent cuts to the public health system add another obstacle.
Tracking and Diagnosing Cyclosporiasis Challenges Health Professionals
By Monday, July 13, 2026, more than 2,500 cases had been confirmed in Michigan, and more than 350 cases had been reported in Ohio, with more than 90 hospitalizations across both states, according to CNN. Although the U.S. Centers for Disease Control and Prevention (CDC) has announced a large multi-state cyclosporiasis outbreak occurring in at least four Midwestern states, it's not yet clear whether all reported cases are part of the same outbreak and therefore trace back to a single source.
Cyclosporiasis rarely spreads directly between people. Instead, it usually results from consuming contaminated food, most commonly fresh produce, or contaminated water. Typical symptoms include watery diarrhea, stomach cramps, and bloating lasting several days. In severe cases, dehydration caused by ongoing diarrhea can lead to hospitalization.
Since Cyclospora, the parasite that causes cyclosporiasis, is highly resilient, it can survive on foods for weeks. Combined with people waiting out their symptoms at home instead of seeing a doctor, along with the elaborate testing required for diagnosis, accurately estimating case counts is particularly challenging.
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Not All Surveillance Systems Include Tracking Cyclospora Anymore
To track the spread of foodborne pathogens, scientists can use genomic testing, comparing the DNA of pathogen strains from sick people with those found in contaminated food or water to help identify links between cases.
However, this method is primarily designed for tracking bacteria, such as E. coli and Salmonella. Cyclospora, by contrast, is a far more complex parasite that is harder to monitor through genetic testing.
Besides these technical challenges, experts also point to recent cuts to public health surveillance systems as another obstacle. As reported by CNN, the FoodNet system, a collaborative U.S. public health program, reduced the number of pathogens it routinely monitors from eight to two in July 2025, excluding Cyclospora despite its status as a nationally notifiable disease.
Although cyclosporiasis cases are expected to rise during the summer and are still being tracked through other surveillance systems, according to a U.S. Department of Health and Human Services spokesperson on CNN, other experts have voiced concerns that cutting programs could hamper the early detection of outbreaks.
First Evidence Points to Lettuce and Salad Greens as the Outbreak's Origin
In the case of cyclosporiasis, time is the public health professionals' biggest enemy. By the time a case can finally be confirmed, several weeks have often passed since the patient became infected.
Although there hasn't been a nationwide recall of any food items, Michigan's Department of Health and Human Services says current findings from its investigation point to lettuce or salad greens as a potential source of the outbreak. Officials recommend purchasing whole heads of lettuce instead of pre-washed produce and thoroughly washing and cooking food before consumption.
As symptoms take time to develop and investigators are still interviewing patients about what they ate weeks earlier, the investigation into the source of the cyclosporiasis outbreak remains ongoing.
This article is not offering medical advice and should be used for informational purposes only.
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Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- This article references information from CNN: Michigan says diarrhea outbreak may be linked to lettuce, salad greens as cases rise above 3,000
- This article references information from the CDC: Cyclosporiasis Outbreak with Unknown Source
- This article references information from the Michigan Department of Health and Human Services: MDHHS updates recommendations for cyclosporiasis prevention
