A parasitic illness tied to contaminated produce is spreading across 17 states this summer, and physicians are issuing an increasingly urgent warning: most infected patients are never properly diagnosed because routine stool cultures used in most clinical labs do not test for this specific organism.
The Centers for Disease Control and Prevention has confirmed 145 domestically acquired cases of Cyclosporiasis — illness caused by the parasite Cyclospora cayetanensis — in 17 states since May 1, 2026. Twenty of those patients have been hospitalized. No deaths have been reported. But public health officials and independent analysts widely agree that the confirmed count substantially understates the true burden of illness.
Michigan, which was not part of the CDC's original 17-state count, has now reported more than 150 cases across seven counties on its own — suggesting the national case total may already be in the hundreds. The FDA and CDC continue to search for the contaminated food source, which has not been identified as of this writing.
Why This Matters
Cyclospora is one of the most diagnostically elusive foodborne pathogens in the United States clinical system — not because it is rare, but because of how the standard clinical response to gastrointestinal illness is structured.
When a patient presents with prolonged diarrhea, a clinician typically orders a routine stool culture. Standard stool cultures test for common bacterial pathogens like Salmonella, Campylobacter, and E. coli. They do not automatically test for Cyclospora. Detecting the parasite requires a specific laboratory request — either an ova and parasite examination with special staining techniques or a direct Cyclospora-specific test. Most primary care physicians and even many emergency physicians do not reflexively order this additional testing for gastrointestinal illness.
The result is that patients with Cyclospora illness frequently go weeks without a correct diagnosis, receiving symptomatic treatment that does not address the underlying parasite. Unlike bacterial foodborne illness, Cyclosporiasis does not resolve on its own in most cases and can last several weeks or return in cycles if left untreated.
What We Know So Far
CDC's surveillance data, current through June 16, 2026, show:
- 145 confirmed domestically acquired cases in 17 states (the true count is likely substantially higher)
- Illness onset dates : May 1 through June 7, 2026
- Median illness onset : May 19, 2026
- Age range : 5 to 86 years (median age 42)
- Gender : 61% female
- Hospitalizations : 20 confirmed
- Deaths : None reported
- Food source : Not yet identified; investigation ongoing
The FDA's outbreak investigations table lists the Cyclospora investigation as active, with multiple clusters under traceback investigation.
None of the 145 confirmed patients reported international travel in the two weeks before becoming ill, confirming these are domestically acquired infections linked to a U.S. food source.
Where the Risk Is Highest
New York has reported the highest state case count, with between 31 and 80 confirmed infections, according to Newsweek's analysis of CDC data. Illinois and Texas have each confirmed between 11 and 30 cases, making them the only other states reporting more than 10 infections.
Additional confirmed cases have been reported in Alaska, Colorado, Connecticut, Florida, Georgia, Louisiana, Massachusetts, New Jersey, North Carolina, Ohio, Pennsylvania, Tennessee, Virginia, and Wisconsin.
Michigan is a significant emerging concern. CBS Detroit reported that an investigation into Cyclospora has expanded into seven Michigan counties, with more than 150 local cases, a figure that exceeds the confirmed counts in any individual state in the CDC's formal count and was not included in the agency's 17-state tally.
Historically, Cyclospora outbreaks in the United States have been linked to fresh produce imported from Mexico and Central America — particularly cilantro, basil, bagged salad mixes, arugula, and leafy greens. No specific product or supplier has been confirmed in the current investigation.
What Doctors and Experts Say
Public health officials and clinicians responding to the outbreak have consistently emphasized the same message: if a patient presents with prolonged or recurring watery diarrhea lasting more than a few days, and the illness cannot be explained by common bacterial causes, the clinician should specifically order Cyclospora testing — because standard stool cultures will miss it.
The CDC's clinician guidance specifically notes that Cyclosporiasis is reportable in 47 states and the District of Columbia, and that health care providers should contact local health departments about potential cases and clusters so public health authorities can take action to prevent additional infections.
The infection is treated effectively with the antibiotic combination trimethoprim-sulfamethoxazole, sold under the brand name Bactrim. Without treatment, symptoms can last anywhere from a few days to more than a month and frequently return in cycles as the parasite continues to reproduce in the intestinal tract.
What the Evidence Shows — and What It Does Not
The CDC has explicitly stated that there is no evidence of a single, unified multistate outbreak linking all 145 cases. Instead, the surveillance data reflects a count of domestically acquired Cyclospora infections across the country during the normal summer peak season for the parasite — May through August — with multiple clusters under separate traceback investigations.
This distinction matters for consumers: there is no single food product that has been identified, recalled, or linked to confirmed illness. Without a specific recall, public health guidance remains focused on general produce safety practices rather than a specific item to avoid.
The true case count is widely understood to be higher than what is officially confirmed. The CDC's own surveillance notes acknowledge that many cases go unreported because infected individuals recover without medical care or are never tested. The Michigan situation — with 150 locally tracked cases not included in the CDC's 17-state count — illustrates this undercount problem concretely.
Who Faces the Greatest Risk?
Cyclospora infections can affect people of any age and background who consume contaminated produce. Certain groups are more vulnerable to prolonged illness:
- Immunocompromised individuals (organ transplant recipients, people living with HIV, cancer patients on chemotherapy)
- Adults who consume large quantities of fresh leafy greens, herbs, and salads regularly — the categories most historically linked to Cyclospora outbreaks
- People traveling to or returning from tropical and subtropical regions where Cyclospora is endemic, including parts of Latin America, South Asia, and the Caribbean
Symptoms and Warning Signs to Watch For
The hallmark symptom of Cyclosporiasis is frequent, sometimes explosive watery diarrhea that may wax and wane over days to weeks. Additional symptoms typically include:
- Stomach cramping and bloating
- Nausea and vomiting
- Loss of appetite and weight loss
- Fatigue and muscle aches
- Low-grade fever
- Burping (flatulence)
Symptoms typically begin within 2 to 14 days of consuming contaminated food or water. Unlike many foodborne illnesses that resolve in a few days, Cyclosporiasis often persists for weeks, and symptoms may disappear and reappear multiple times if untreated.
Critical note: If you have had prolonged, recurring watery diarrhea lasting more than a week and routine stool tests came back negative, specifically ask your doctor about Cyclospora testing. The illness will not appear on a standard stool culture.
What You Can Do Now
- Wash all fresh produce thoroughly under running water before eating. Scrub firm produce with a clean brush. This reduces but does not eliminate Cyclospora risk, as the parasite can be difficult to remove from leafy surfaces. Note that Cyclospora is not killed by routine chemical disinfection.
- If you develop prolonged watery diarrhea , contact your health care provider. Mention that Cyclospora is currently circulating and specifically ask whether Cyclospora testing is indicated.
- Do not self-treat with over-the-counter antidiarrheal medications as a substitute for diagnosis. If the cause is Cyclospora, antibiotic treatment is needed.
- If you are immunocompromised , be especially cautious with fresh herbs and leafy greens purchased in bulk or from salad bars during active investigation periods.
- Report illness to your local health department. Reporting confirmed or suspected cases helps public health officials identify clusters and trace contamination sources more quickly.
Cost and Access: What Patients Should Know
Testing for Cyclospora requires a specific laboratory request. Standard stool culture kits available at most physician offices and emergency rooms will not automatically include Cyclospora testing. Patients may need to ask their provider explicitly for an "ova and parasite examination" or a specific Cyclospora PCR test.
Treatment with trimethoprim-sulfamethoxazole (Bactrim/Septra) is inexpensive and widely covered by most insurance plans. Generic versions are typically available at a cost of under $10 at most pharmacies with a GoodRx discount.
Community health centers and urgent care clinics can order Cyclospora-specific stool testing; patients without a primary care provider can access testing through their local health department.
What Happens Next
The FDA and CDC will continue the traceback investigation until a contaminated food source is identified or all leads are exhausted. Based on prior outbreak patterns, investigators are likely examining fresh herb and leafy green supply chains with distribution to affected states.
The summer Cyclospora season in the United States runs through August 31, meaning additional cases are expected in the coming weeks. The CDC updates its case count weekly during the active surveillance period. MedicalDaily will report when a food source is identified or a recall is issued.
The Bottom Line
Cyclospora illness is spreading across at least 17 states this summer, with New York, Illinois, Texas, and Michigan seeing the heaviest concentrations. The largest barrier to treatment is not the lack of an effective antibiotic — it is the fact that most clinical labs do not test for this parasite unless specifically asked. If you or a family member has experienced prolonged, recurring gastrointestinal illness this summer and routine tests have been negative, talk to your provider about Cyclospora-specific testing.
