A customer shops for cilantro at a Walmart Supercenter on July 23, 2026 in Austin, Texas. Brandon Bell | Getty ImagesThe nation's largest multistate outbreak of cyclosporiasis linked to shredded iceberg lettuce has expanded to nine states, the Centers for Disease Control and Prevention said Friday.The four newly linked states – Illinois, Kansas, Oklahoma and Pennsylvania – join Indiana, Kentucky, Ohio, West Virginia and hard-hit Michigan. Cyclospora is a microscopic parasite that typically infects people through contaminated food or water and causes cyclosporiasis, a gastrointestinal illness that can result in symptoms including severe diarrhea. Patients can require hospitalization, but no deaths have been recorded related to the parasite this year.The outbreak is already the largest of cyclosporiasis reported in the U.S. this year, with thousands of illnesses recorded nationwide. That is well above the roughly 200 to 1,000 cases typically reported annually. Meanwhile, the Food and Drug Administration is investigating a separate cyclosporiasis outbreak linked to an unidentified food product or products. The U.S. is trying to investigate the sources of the parasite and contain its spread amid confusion over its response to the outbreak and staffing cuts that some experts say made it harder to curb it. U.S. health and food regulators have zeroed in on shredded iceberg lettuce supplied by Taylor Farms. Mexican health authorities on Thursday said that samples of lettuce and water from Taylor Farms' plant in central Mexico tested negative for cyclospora. However, that result does not disprove the Food and Drug Administration's earlier identification as Taylor Farms de Mexico as the likely source of the outbreak. The earliest cases began showing symptoms in mid-May. Moreover, the long incubation period for infection means that the crop responsible would have been distributed weeks ago.Last week, the FDA said that the produce giant supplied the shredded iceberg lettuce to the Taco Bell restaurants where people ate before becoming ill. Taylor Farms also issued a voluntary recall for all iceberg lettuce sourced from its Guanajuato, Mexico facility, and Taco Bell pulled the affected lettuce from its restaurants.The CDC has so far tallied 1,947 people infected with cyclospora who also reported eating at Taco Bell in the nine states. Illnesses in the outbreak tied to iceberg lettuce began on June 22 and have continued through July 20, the CDC said. The federal count has lagged behind state tallies, so some of the states hit by the outbreak have reported much higher numbers of infections.But Taylor Farms has drawn criticism for its response to the outbreak. Some health experts blasted its recall notice, which included abbreviations and did not allow consumers to understand easily if they had bought or eaten any product that was at risk. After the FDA reported a false positive of lettuce samples from Taylor Farms on Sunday, the company issued a statement saying that the health agency had apologized. The FDA later clarified that it had not apologized to Taylor Farms, and the company deleted the statement on X, although it is still available on its website. The agency also said it still considered the company's iceberg lettuce the likely source of the outbreak.Taylor Farms supplies lettuce and other produce to major retailers such as Walmart, Target and Whole Foods, as well as restaurant chains including Taco Bell.