Federal health officials have expanded their investigation into a multistate outbreak of cyclosporiasis linked to contaminated iceberg lettuce, now spanning 15 states. The Centers for Disease Control and Prevention (CDC) previously connected cases in nine states to the outbreak on July 24. Since then, additional illnesses have emerged in Illinois, Indiana, Kansas, Kentucky, Michigan, Ohio, Oklahoma, Pennsylvania, and West Virginia.

The outbreak has been traced to shredded iceberg lettuce produced by Taylor Farms de Mexico. The company issued a recall of the product on July 17 after epidemiological and trace-back investigations connected the lettuce to illnesses reported among consumers dining at Taco Bell. The recalled lettuce was distributed between June 29 and July 16 through both food-service and retail outlets across 27 states.

While illnesses have been officially linked to 15 states, federal officials continue to investigate reports of cyclospora infections in more than two dozen other states. These additional cases have not yet been tied to Taylor Farms or the recalled lettuce, and the sources of other outbreaks remain under review.

Taylor Farms has not disclosed further details regarding the volume of lettuce involved in the recall or the distribution of the product prior to June 29. Requests for comment from the company have not been immediately answered.

The CDC and Food and Drug Administration (FDA) are collaborating on the investigation, employing detailed interviews with affected individuals to track food consumption patterns, identify the contaminated product, and understand how the contamination occurred. The CDC focuses on identifying the source of the outbreak through patient interviews, while the FDA works to trace the product’s origin and stops further distribution.

Experts caution that new reported cases do not necessarily indicate ongoing risk from the product. The actual number of infected individuals is likely higher than reported figures, as some may recover without medical attention and thus go untested. Additionally, cyclospora’s incubation period can extend up to six weeks, meaning recent cases may not yet be fully accounted for.

“The challenge is assessing the current risk, such as whether it’s still safe to eat salad,” said Craig Hedberg, a professor in the University of Minnesota’s Division of Environmental Health Sciences.

Authorities continue to monitor the situation closely and advise consumers to heed recall notices and practice food safety precautions to reduce the risk of infection.