Federal authorities are investigating a widespread outbreak of cyclosporiasis, a parasitic gastrointestinal illness that has sickened thousands across 34 states since May 1, 2026. Linked to contaminated produce, the outbreak has resulted in at least 1,645 confirmed domestic cases, with officials identifying shredded iceberg lettuce from central Mexico as a primary source.
The Scope of the Cyclospora Outbreak
The current surge in cases represents a significant uptick in domestic cyclosporiasis, a condition caused by the microscopic Cyclospora parasite. According to the Centers for Disease Control and Prevention (CDC), the number of confirmed cases is substantially higher than the 249 reported during the same period in 2025. While 1,645 cases have been officially confirmed as domestically acquired, the agency is aware of more than 5,100 additional reports that require further analysis to confirm the illness as domestically acquired cyclosporiasis. Of the 1,645 case-patients with available information, 141 individuals, or 9%, were hospitalized. No deaths have been reported.
The impact is geographically broad, affecting 34 states, but the Midwest remains the epicenter. Michigan has reported the most cases of any state, with more than 5,000 cases reported as of Thursday, according to the state’s Health and Human Services department. More than 100 people have been hospitalized in Michigan alone. Within the state, the Detroit area is a hot spot, with Wayne County reporting nearly 600 cases as of Thursday. Oakland County, located northwest of Detroit, reported just shy of 400 cases, while Ingham County—home to the state capital, Lansing, and Michigan State University—also reported about 400 cases.
In Illinois, health officials have reported 216 cases with 18 hospitalizations. In Indiana, the Department of Health reported 366 cases as of Friday, with the Indianapolis and Fort Wayne areas leading the state with 40 cases each. Kentucky has reported 108 confirmed cases with seven hospitalizations, according to the Kentucky Department for Public Health. Jefferson County, home to Louisville, has the highest number of cases in that state.
Dr. Alfredo Mane Lora, an infectious disease expert at St. Anthony Hospital, told WGN that the official counts likely represent only a fraction of the total infections. When we look at 200 cases in Illinois, this is the tip of the iceberg, because these are the folks that did seek care. A lot of individuals that develop this either have mild symptoms or it self-resolves,
Dr. Mane Lora said.
Identifying the Source: Lettuce and Supply Chain Disruptions
Investigators have narrowed the focus of their search for the origin of the parasite. Federal authorities have linked shredded iceberg lettuce from a Mexican supplier for Taco Bell restaurants in five states to the outbreak. The CDC identified Kentucky, Indiana, Michigan, Ohio, and West Virginia as states where Taco Bell locations were served the contaminated lettuce. On Friday, Taylor Fresh Foods announced it was removing all of its iceberg lettuce sourced from central Mexico from the U.S. market.
The difficulty in pinpointing the source stems from the parasite’s nature and the complexities of food distribution. Cyclospora has a lengthy incubation period; the time from exposure to the development of watery diarrhea symptoms can be as long as two weeks. This makes trackback work—figuring out everything a patient ate during the incubation period—a difficult task. Furthermore, because Cyclospora is a protozoan parasite, laboratory detection in stool can be challenging, and standard ova and parasite exams may not detect it reliably.
Clinical Challenges and Public Health Guidance
Cyclosporiasis is a gastrointestinal illness that can last from a few days to a month or longer. The most common symptoms include frequent watery diarrhea, loss of appetite, weight loss, bloating, nausea, and fatigue. Less common symptoms include low-grade fever and vomiting. Complications can include malabsorption, cholecystitis, and reactive arthritis.
In Ohio, which reported 171 cases and 28 hospitalizations as of July 2, health officials are emphasizing prevention. Ohio Department of Health Director Bruce Vanderhoff encouraged residents to thoroughly wash fruits and vegetables. Fortunately, there have been no deaths in Ohio, as is consistent with our past experiences with this illness,
Vanderhoff stated in a July 2 release.
As the investigation continues, the CDC, the U.S. Food and Drug Administration (FDA), and state and local health departments are working to reconcile reporting discrepancies. The CDC notes that federal case counts have lagged behind numbers reported by individual states, partly due to the time required to confirm if cases are domestically acquired and the fact that cyclosporiasis is often underdiagnosed and underreported.
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