Alert: Cyclospora cayetanensis: Multistate Outbreak with Midwest Epicenter
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Jul 8, 2026
5 min read
alert
Alert: Cyclospora cayetanensis: Multistate Outbreak with Midwest Epicenter
Gage Moreno
Caitlin Rivers
FOI Clinical issues two types of rapid communications: alerts for highest priority information, and advisories for emerging events clinicians should be aware of. This is an alert .<br>Situation Summary<br>A rapidly expanding multistate Cyclospora cayetanensis outbreak has its epicenter in southeast Michigan and northwest Ohio, according to current reports. As of July 8, Michigan has received more than 700 reports of cyclosporiasis, including 38 hospitalizations since June 22. This is approximately 14 times the state's annual average. Ohio reports 177 cases across 43 counties (last updated July 7, per ODH spokesperson), with spread throughout central and northwest Ohio.<br>The effects extend beyond the Midwest. At least 18 states are affected nationally; aggregated state-level reporting suggests a true national burden well above 1,200 cases, far outstripping the CDC's most recent tally (145 cases as of June 16, now outdated).<br>No food source has been identified and no FDA recall has been issued. Traceback efforts to identify the source are underway.<br>Epidemiological Situation<br>Case distribution (as of July 8, 2026)<br>Note on national totals: The CDC surveillance report (145 cases as of June 16) does not include more recent data. Michigan's >700 cases alone exceed the national CDC count by nearly 5-fold. Aggregated state health department data suggests a true national burden of at least 1,200 cases as of July 8.
State<br>Cases<br>Hosp.<br>Last updated
Michigan<br>>700<br>38<br>July 8
Ohio<br>177<br>July 7
Illinois<br>141<br>~July 6
New York<br>120<br>~July 7
North Carolina<br>110+<br>~July 6
Indiana<br>72<br>~July 6
Texas<br>48<br>~July 6
11+ additional states<br>Various
Michigan epicenter<br>Monroe County leads with 173 confirmed cases, followed by Washtenaw (95), Lenawee (86), and Wayne (58) counties. The ProMedica Health System, whose clinical footprint spans the Michigan-Ohio border, reports having treated 411+ confirmed Michigan cases. Illness onset has been concentrated since late June 2026.<br>Subscribe to FOI Clinical<br>Pathogen Background<br>Cyclospora cayetanensis is an intestinal coccidian protozoan parasite that infects the small intestinal epithelium, causing profuse watery diarrhea with a characteristic relapsing course. Transmission is exclusively fecal-oral via ingestion of food or water contaminated with sporulated oocysts. Person-to-person transmission does not occur. Cyclospora requires days to weeks of environmental sporulation before becoming infectious.<br>Previous U.S. outbreaks have been linked to fresh produce with complex supply chains, particularly:<br>Bagged salad kits and mixed leafy greens<br>Fresh basil and cilantro<br>Raspberries<br>Snow peas and scallions<br>Contamination typically occurs at the farm or irrigation level, making traceback investigations difficult. Cyclospora oocysts are resistant to standard chlorination and survive on produce that passes visual inspection.<br>Rinsing of produce is unlikely to be effective according to FDA, but is nonetheless recommended by CDC. A brief review of the literature by FOI Clinical found very little evidence. We conclude that washing may reduce but does not eliminate risk.<br>Clinical Guidance<br>Presentation
Feature<br>Details
Incubation<br>2–14+ days; average ~7 days
Cardinal symptom<br>Watery, often explosive diarrhea, frequent bowel movements, often debilitating at peak
Associated symptoms<br>Profound fatigue, anorexia, weight loss, low-grade fever, nausea, bloating, abdominal cramping
Course<br>Characteristically relapsing. Periods of relative improvement alternating with recurrence; may persist weeks to months untreated
Severity<br>Debilitating in immunocompetent hosts; substantially more severe in immunocompromised patients (HIV/AIDS with low CD4, organ transplant, active chemotherapy)
The hallmark presentation is prolonged watery diarrhea with disproportionate fatigue and anorexia. Patients commonly present after weeks of symptoms, often having been told their workup was negative because standard stool panels do not test for Cyclospora (see Diagnosis below). Cyclosporiasis is commonly misdiagnosed as IBS, post-infectious IBS, or nonspecific colitis.<br>Diagnosis<br>The default panel for a standard stool workup at most U.S. institutions includes bacterial culture (Salmonella, Shigella, Campylobacter, E. coli), C. difficile testing, and an ova and parasite (O&P) examination. None of these reliably detect Cyclospora cayetanensis. Moreover:<br>Routine stool wet preparation does not detect Cyclospora<br>Standard O&P misses Cyclospora unless the lab specifically...