The US Centers for Disease Control and Prevention reported on July 22, 2026, that more than 4,100 people have been infected with cyclosporiasis across 41 states. The illness is caused by a tiny parasite — a microscopic organism that lives in the intestines — called Cyclospora cayetanensis. So far, 308 people have been hospitalized, and no deaths have been recorded. The agency cautioned that another 7,400 suspected cases remain under review and that the total is likely to rise. The figures, published via Al Jazeera and credited to Reuters and the Associated Press, show a sharp jump from the 1,644 cases the CDC had reported just four days earlier. In Michigan alone, state health officials counted over 6,000 cases by July 20.

The CDC identified shredded iceberg lettuce served at Taco Bell as the food carrying the infection, in a July 18 advisory covering five states: Indiana, Kentucky, Michigan, Ohio, and West Virginia. Taco Bell had begun pulling ingredients from some locations as early as July 8. The outbreak's link to a single national restaurant chain has had immediate commercial consequences. Foot traffic at restaurant chains declined following the outbreak, according to Reuters, and the food distributor Sysco pulled iceberg lettuce from distribution. Wendy's and Chipotle publicly stated they were not affected.

The investigation has centered on Taylor Farms, a company that grows lettuce in Mexico and exports it to US shops and restaurants. On July 17, Taylor Farms recalled its iceberg lettuce. The company's Mexican branch, Taylor Farms de Mexico, is based in Guanajuato, in central Mexico. The FDA — the US agency responsible for regulating food safety — assigned outbreak reference number #1390 to the investigation and began testing and tracing the lettuce supply after formally announcing its probe on July 16. US investigators have pointed to Taylor Farms' Mexican facilities as a likely source, though the evidence has been anything but straightforward.

Over three consecutive days, the FDA issued shifting and at times contradictory information. On Saturday, the agency said a sample of Mexican lettuce from Taylor Farms tested positive for the parasite. On Sunday, it said the result was a false positive — a test that looks like it found the parasite, but actually did not. On Monday, the agency said its investigation continues to point to Taylor Farms' Mexican facilities as the source. Taylor Farms issued a statement noting that "at this moment, FDA has not identified a single positive product test result for Cyclospora," as reported by ABC News. NPR reported on July 20 that the FDA remained focused on Taylor Farms lettuce as the likely source despite the retracted test.

Complicating the picture further, an FDA official named Diamantas disclosed that the agency has been investigating five separate clusters of illness nationwide since the seasonal rise in infections began in May. A cluster is a group of similar illnesses traced to a common source. Rather than one single outbreak, federal health officials are examining five distinct clusters. That means the Taco Bell-linked cases in the five-state advisory may be only one piece of a broader seasonal pattern. Cyclosporiasis infections typically peak in the summer months.

Mexican authorities have pushed back against the US framing. On July 22, Mexican Secretary of Health David Kershenobich disputed the US findings, stating there was no evidence the outbreak originated in Guanajuato, where authorities are conducting their own investigation. Mexico's agri-food safety agency, SENASICA, had been tracking the situation for over a week before Kershenobich's statement. A SENASICA bulletin dated July 14 documented Michigan health officials' suspicion that lettuce or salad greens were the source. A July 17 bulletin covered the five-state outbreak linked to iceberg lettuce, and a July 20 bulletin reported that the United States had recalled iceberg lettuce from Mexico due to possible contamination with the parasite. The Mexican Senate's press summary on July 15 also cited the Michigan health department's statement about lettuce as a potential source.

The Associated Press reported that Taylor Farms has been tied to foodborne outbreaks in the past, a detail that has sharpened scrutiny of the company's Mexican operations. Yet neither US nor Mexican testing has produced a confirmed positive result from an actual lettuce sample. The parasite itself is killed when food is heated to 158 degrees Fahrenheit or higher. But lettuce is eaten raw, so there is no point in the production process where heat destroys the organism before it reaches the consumer.

The broader context here is a multi-agency investigation in which three US bodies (the CDC, the FDA, and state health departments) and two Mexican agencies (the Secretary of Health and SENASICA) are working with different standards of evidence and reaching different conclusions about where the outbreak started. The FDA can identify a probable source by tracing where sick people ate and where the food came from, even without a lab test confirming the parasite on the food itself. Mexican authorities, by contrast, want product-level laboratory proof before accepting that the outbreak started on their soil. This kind of disagreement is a recurring problem in cross-border food safety investigations involving produce grown in Mexico and consumed in the United States. With 7,400 suspected cases still under CDC review and the seasonal window for these infections typically extending through August, the case count and the diplomatic disagreement are both likely to grow before this resolves.