The outbreak of Cyclospora cayetenensis infections continues to grow in Midwestern U.S. states, with Michigan and Northwestern Ohio public health officials respectively reporting 6,571 and 2,029 cases as of July 21.

Meanwhile, the U.S. Centers for Disease Control and Prevention (CDC), which has not updated its counts since July 14, reports an outbreak of more than 1,644 confirmed, domestically acquired cyclosporiasis cases across five states: Michigan, Ohio, West Virginia, and Indiana. Patients fell ill after May 13, 2026.

Case Count Confusion

State case counts are higher than CDC’s because states may be reporting both probable and confirmed cases, and there is also a lag between the time a state receives notice of a case and when CDC confirms cases reported by states as domestically acquired and connected to the outbreak.

While the number of Cyclospora infections in the U.S. is certainly elevated compared to previous years, that does not mean all cases are linked. According to a media call with U.S. Food and Drug Administration (FDA) Acting Commissioner Kyle Diamantas, as reported by Food Fix, the agency has investigated five different subclusters since the start of the Cyclospora season in May, three of which are already considered over (without a source being publicly identified). Additionally, aside from the large Midwestern outbreak cluster, FDA is currently investigating two other cyclosporiasis outbreaks, per the agency's Coordinated Outbreak Response and Evaluation (CORE) table.

U.S. Sees 6.6 Times More Cyclosporiasis Cases So Far in 2026 Than in 2025

Although the prevalence of C. cayetanensis has had an upward trajectory in the U.S. over the last three decades, the number of cyclosporiasis cases reported so far in 2026 greatly surpasses that of previous years. For example, domestic cases of Cyclospora infections have risen from 537 in 2016 to nearly 3,000 in 2023.¹ Additionally, by this time in 2025, CDC only received 249 reports of domestically acquired cyclosporiasis cases—meaning, in 2026, per CDC's latest counts, the U.S. is so far experiencing a 6.6-fold increase in cases.

In a July 16 media briefing held by George Washington University’s Institute for Food Safety and Nutrition Security, leading public health academics posited that the staggering number of cases in 2026 could be a symptom of a strained national outbreak surveillance system. They also suggested that increased adoption of improved diagnostic tests could contribute to the identification of more cases than would have been identified in years past. Separately, some Cyclospora experts have suggested that longer, hotter summers driven by climate change could play a role in the growing prevalence of the seasonal parasite.^2,3

Signs Point to Taylor Farms Lettuce

Based on traceback investigations, the U.S. Food and Drug Administration (FDA) has identified iceberg lettuce grown in Central Mexico and supplied by Taylor Farms of Mexico, which was distributed to 28 states by parent company Taylor Fresh Foods, as the source of the outbreak.

Taylor Farms has issued a voluntary recall. Downstream firms that received implicated lettuce and offered it for sale include Taco Bell (which has stopped using Taylor Farms as a lettuce supplier) and Walmart.

Epidemiological evidence also points to Taylor Farms. The 1,600-plus CDC-confirmed outbreak patients reported exposure to Taco Bell. Additionally, Michigan officials analyzed food exposure details from 190 of its CDC-confirmed outbreak cases and found that 90 percent of those interviewed reported eating iceberg lettuce at Taco Bell.

FDA False Positive Does Not Negate Other Evidence

Interestingly, on July 18, FDA reported that a sample of lettuce supplied by Taylor Farms had tested positive for C. cayetenensis, but on July 19, the agency said this finding was more likely a false positive. Based on strong epidemiologic and traceback evidence, however, Taylor Farms is still considered to be the source of the outbreak.

Alex Sundermann, Dr.P.H., Assistant Professor of Epidemiology at the University of Pittsburgh, who is known for disseminating public health information on social media, explained to Food Safety Magazine why the false positive result does not cast doubt on Taylor Farms' implication in the outbreak.

"Outbreak investigations rely on a toolkit, and epidemiology and environmental sampling are two different tools that answer two different questions. Epidemiology asks: who got sick and what did they have in common? That evidence, gathered by public health investigators, pointed clearly to lettuce from a single supplier well before FDA ever collected a sample," Dr. Sundermann said.

He continued, "Environmental sampling asks something narrower: is the pathogen present in this specific piece of food at this specific moment? A positive can help confirm a source, but a negative doesn't clear one. It just means the pathogen wasn't detected in that sample or at that time. Given that Cyclospora can't be cultured and this sample was taken weeks after implicated lettuce was already consumed, a negative here is not surprising and not exonerating. The epidemiologic and traceback evidence haven't changed."

Given the difficulty of testing for C. cayetenensis, traceback evidence is especially imperative in the current outbreak, explained Michelle Covey, Vice President of Customer Success at GS1 US. “Events like this underscore why traceability and supply chain visibility are essential to food safety," she told Food Safety Magazine. "During an outbreak, investigators need reliable, consistent data to quickly connect products, lots, locations, and movement through the supply chain."

References

1. Keener, L. “Cyclospora cayetanensis: An Emergent Public Health Threat and an Enigma for Traceback Investigation.” Food Safety Magazine (October 2025). https://www.food-safety.com/articles/10770-cyclospora-cayetanensis-an-emergent-public-health-threat-and-an-enigma-for-traceback-investigation.
2. Avlonitis, M. “The Cyclospora outbreak was predictable and preventable, an expert says.” WUSF (July 2026). https://www.wusf.org/health-news-florida/2026-07-14/cyclosporiasis-outbreak-explosive-diarrhea-predictable-preventable.
3. American Community Media. “Could Climate Change Be a Contributor to an Extended Cyclospora Outbreak?” The San Diego Voice & Viewpoint (July 2026). https://sdvoice.info/climate-and-cyclospora/.