Public health officials are investigating a surge in cyclosporiasis cases across the United States, with Michigan reporting nearly 1,000 confirmed infections. While the source of the current outbreak remains unidentified, health agencies link the parasitic illness to contaminated fresh produce and emphasize that the infection is not typically transmitted person-to-person.
Michigan Outbreak and National Case Trends
A parasitic infection caused by the Cyclospora cayetanensis parasite has reached significant levels in Michigan, where state health officials have confirmed 992 cases. This surge represents one of the largest outbreaks of the illness in the state’s history. The Michigan Department of Health and Human Services (MDHHS) confirmed that while 40 hospitalizations have occurred, no deaths have been linked to the outbreak.
Nationwide, the data shows a broader rise in infections. The Centers for Disease Control and Prevention (CDC) has tracked at least 145 cases across 17 states as of June 16, though experts suggest these figures likely undercount the true total. In Maryland, health authorities have recorded 32 cases in 2026, with 28 of those appearing since May 1. Ohio has also seen a sharp increase, with 177 cases reported by early July.
Symptoms and Medical Challenges
Cyclosporiasis is distinct from typical bacterial food poisoning, often leading to prolonged gastrointestinal distress. The CDC describes the most common symptom as watery diarrhea with frequent and sometimes explosive bowel movements. Other symptoms include nausea, stomach cramps, fatigue, and loss of appetite.
The illness can persist for weeks or even months if left untreated, and patients often face a delayed diagnosis. "Unless you get a stool test, specifically a GI pathogen panel and it comes back positive, a doctor will not know how to treat it. Without the test, it could be viewed as bacterial or viral diarrhea," said Dr. Anil Sharma, an associate professor in the Division of Gastroenterology, Hepatology & Nutrition at the University of Florida College of Medicine.
For more on this story, see Michigan Cyclosporiasis Cases Surge to Over 700 in Unusual Parasitic Outbreak.
Treatment requires specific antibiotics, such as Bactrim DS. "You have to treat this infection with an antibiotic and there is a special antibiotic called Bactrim DS," Sharma added. Because symptoms can take anywhere from two days to two weeks to manifest, investigators face significant difficulty tracing the specific source of contamination.
Transmission Risks and Prevention Strategies
The parasite spreads through the fecal-oral route, usually via contaminated food or water. "A fecal-oral transmission, meaning it comes from stool that then contaminates food sources and then gets into another person’s system," explained Dr. Jonathan Thierman, president of Expresscare Urgent Care Centers.
Fresh produce is the primary vehicle for the parasite, particularly items with complex surfaces that are difficult to sanitize. "Most typical contaminants are fresh produce, and so they’ve seen it in lettuce, they’ve seen it in berries, I think raspberries is one of the most significant, because it’s the most difficult to wash because there’s a lot of crevices," Thierman noted.
This follows our earlier report, Michigan sees 170+ cyclosporiasis cases in weeks, tripling annual average.
- Lettuce: Remove the outer two or three layers of leaves and wash the inner leaves thoroughly under running water.
- Herbs: Thoroughly wash cilantro and basil under running water, separating the leaves to ensure debris is removed.
- Green Onions: Trim the root ends and remove the outer layers of the green onions before rinsing.
- Berries: Raspberries are difficult to clean due to their texture; officials suggest cooking them into pies or jams for the highest level of safety.
- General Produce: Scrub firm items like melons and cucumbers with a clean brush, and sanitize all cutting boards and food-prep surfaces.
Experts caution that while washing helps, it does not eliminate the risk entirely. Melanie Firestone, a foodborne illness researcher at the University of Minnesota, told The Associated Press that there is significant underreporting for this condition because standard food poisoning tests are often not designed to detect the Cyclospora parasite.
Read also: Lucas County Leads Ohio in Cyclosporiasis Cases.
Investigation Status and Seasonal Context
The current surge aligns with the typical cyclosporiasis season, which runs from May 1 through August 31. Despite the high case numbers, federal and state agencies have not identified a single nationwide source of contamination. "The source of the outbreak has not been identified, and MDHHS continues to work with local health departments and partners to investigate cases and provide updates as more information becomes available," the state department stated.
Historically, the United States has faced larger outbreaks, such as a 2019 event linked to Mexican basil that sickened more than 2,400 people, and a 1997 outbreak tied to Guatemalan raspberries that sickened more than 1,000 people. Health officials continue to monitor the situation, urging residents to remain vigilant with food hygiene even in regions where case counts remain lower.
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