Health authorities in the United States have identified a connection between a parasitic illness outbreak in 15 states and iceberg lettuce. The Centers for Disease Control and Prevention (CDC) announced that the number of states linked to this severe outbreak has increased from nine to 15, now including Arkansas, Iowa, Missouri, Nebraska, New Hampshire, and North Carolina. Earlier, the list comprised Illinois, Indiana, Kansas, Kentucky, Michigan, Ohio, Oklahoma, Pennsylvania, and West Virginia.

This year has seen reports of Cyclospora cases in at least 47 states. Ongoing investigations aim to determine how many relate to a singular contaminated source. Initially, investigators focused on lettuce served at Taco Bell. The investigation shifted to Taylor Farms, which supplied the outbreak-linked lettuce, prompting a recall of iceberg lettuce cultivated in central Mexico.

There are many challenges in investigating and controlling cyclospora outbreaks, explained Dr. Juan Luis Marquez, medical director of health departments in Washtenaw and Livingston Counties, Michigan. The delay between exposure and symptom onset complicates analysis, Marquez noted.

Adding to the complexity, staff cuts at various levels of public health reduce the available resources and capacity. Cyclospora, a microscopic spherical parasite, commonly causes watery diarrhea with frequent, sometimes explosive, bowel movements. According to the CDC, these outbreaks typically occur in late spring and summer. The parasite affects the bowels, spreading through feces.

Cyclosporiasis, the resulting illness, is less frequent than other foodborne illnesses like salmonella and E. coli. Identifying the specific cause of individual cases often proves difficult. The worst year for U.S. infections was 2019, with approximately 4,700 cases nationally. In stark contrast, this year has already exceeded that number significantly. Michigan alone reported over 12,000 cases, including two fatalities. When combined with reports from other states, the national total exceeds 25,000.

The Food and Drug Administration (FDA) is monitoring five separate ongoing cyclospora outbreaks. The outbreak spanning 15 states is the largest, with no specific product linked to the remaining outbreaks, one of which has affected 115 people.

The Associated Press Health and Science Department’s work is supported by the Howard Hughes Medical Institute’s Department of Science Education and the Robert Wood Johnson Foundation. Content responsibility remains with the AP.