Federal health officials reported on July 24 that the largest known multistate cyclosporosis outbreak linked to shredded iceberg lettuce has spread to nine states as investigators continue to track new cases.
According to the Centers for Disease Control and Prevention, more than 11,500 cases of cyclosporiasis have been reported this season. There are 4,173 confirmed cases, but health officials are still evaluating about 7,400 additional reports to determine whether these illnesses are related to exposure within the U.S. food supply.
Tracing the source of Cyclospora infection is particularly difficult, as health officials continue to investigate and try to piece together information from reported cases, the CDC said. This is mainly due to the fact that whole genome sequences are not available. However, many foods investigated during disease outbreaks contain multiple agricultural ingredients, making tracking difficult as well, the CDC said.
Let’s take a look at cyclosporosis cases in numbers.
Cystoscodia outbreak Linked to 9 states
An outbreak of cyclosporiasis, which has sickened hundreds of Americans with stomach-wrenching parasitic infections, is now linked to nine states, federal health officials say.
Those nine states include Illinois, Indiana, Kansas, Kentucky, Michigan, Ohio, Oklahoma, Pennsylvania and West Virginia, according to the CDC’s July 24 update. Previously, there were only five states involved, including Michigan, which has the highest number of cases.
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States reporting cyclosporosis cases this year
The CDC is tracking at least 7,400 additional reported cases that have not yet been confirmed by a laboratory and are under investigation. The agency said many of these reports came from Michigan and Ohio. According to the CDC, the map below shows where the 4,173 people infected with cyclosporiasis in the United States lived since May 1, 2026.
The CDC’s case numbers can lag the numbers announced by state health officials by up to six weeks due to tracking, verification and reporting processes, the agency said.
Tracking the largest cyclosporosis outbreak in U.S. history
Cyclosporiasis infections usually increase during the warm summer months when fresh foods associated with the parasite are more widely consumed. The National Notified Disease Surveillance System (NNDSS) is monitoring the largest ancyclosporosis outbreak ever recorded in the United States.
More than 8,000 cases of cyclosporosis in Michigan
More than 8,000 cases of cyclosporiasis have been recorded in Michigan, making it one of the notable public health concerns related to foodborne illness in the state. Cyclosporiasis is caused by a parasite Cyclospora caetanensis It is often associated with contaminated fresh fruits and vegetables. Health officials continue to monitor cases and encourage good food safety practices to reduce the risk of infection.
Contributions by Sarah Moniuszko and Mary Walrath-Holdridge
