Federal health officials reported July 24 that the largest known multi-state cyclosporiasis outbreak associated with shredded iceberg lettuce has expanded to nine states as investigators continue to track new cases.More than 11,500 cyclosporiasis cases have been reported this season, according to the Centers for Disease Control and Prevention. While 4,173 infections have been confirmed, health officials are still evaluating about 7,400 additional reports to determine whether the illnesses were linked to exposure within the U.S. food supply.Health officials are working to piece together information from reported cases as the investigation continues, but tracking the source of Cyclospora infections is especially challenging, according to the CDC. This is largely due to the fact that the whole genome sequence isn't available. But tracking has also been made difficult because many foods investigated in outbreaks have multiple produce ingredients, the CDC said.Here's a look at cyclosporiasis cases by the numbers.Cyclosporiasis outbreak linked to 9 statesA cyclosporiasis outbreak, which has left hundreds of Americans with a stomach-churning parasitic infection, has now been linked to nine states, according to federal health officials.Those nine states include Illinois, Indiana, Kansas, Kentucky, Michigan, Ohio, Oklahoma, Pennsylvania and West Virginia, according to an update from the CDC on July 24. Previously, just five states were connected, including Michigan, which accounted for a high number of the cases.Unable to view our graphics? Click here to see them.States reporting cyclosporiasis cases this yearThe CDC is tracking at least 7,400 additional reported cases that have not yet been laboratory confirmed and remain under investigation. Many of those reports have come from Michigan and Ohio, according to the agency. The map below shows where the 4,173 people with cyclosporiasis acquired in the U.S. since May 1, 2026, lived, according to the CDC.The CDC's case numbers can lag by as much as six weeks behind those cited by state health officials, due to tracking, verification and reporting processes, the agency said.Tracking the largest cyclosporiasis outbreak in US historyCyclosporiasis infections usually rise during the warmer summer months, when fresh produce linked to the parasite is more widely consumed. The National Notifiable Diseases Surveillance System (NNDSS) is monitoring what has become the largest cyclosporiasis outbreak ever recorded in the United States.Michigan has more than 8,000 cyclosporiasis casesMichigan has recorded more than 8,000 cases of cyclosporiasis, making it one of the notable public health concerns linked to foodborne illnesses in the state. Cyclosporiasis is caused by the parasite Cyclospora cayetanensis and is often associated with contaminated fresh fruits and vegetables. Health officials continue to monitor cases and encourage proper food safety practices to reduce the risk of infection.CONTRIBUTING Sara Moniuszko and Mary Walrath-Holdridge