A parasitic outbreak linked to contaminated iceberg lettuce has grown to 10,930 confirmed illnesses across 17 states, according to the CDC's outbreak page, last updated August 20. At least 454 people have been hospitalized and two deaths, both in Michigan, have been confirmed. Illness onset dates span June 14 through August 11, meaning new cases are still being reported even as the source has been identified and recalled.
Investigators traced the outbreak to iceberg lettuce grown by Taylor Farms de Mexico, a processor based in central Mexico. In its investigation update, CDC laid out how it got there:
"Epidemiologic and traceback data showed that iceberg lettuce from Taylor Farms de Mexico ... was contaminated with Cyclospora and made people sick."
CDC, Cyclospora Outbreak Investigation Update
Cyclospora cayetanensis is a single-celled parasite that causes cyclosporiasis, an intestinal illness marked by watery diarrhea that can last for weeks if untreated, along with loss of appetite, cramping and fatigue. It spreads through contaminated food or water rather than person to person, and because it requires specialized stool testing to detect, cases are often undercounted or diagnosed late. CDC's laboratories used genotyping — distinct from full genome sequencing, but sufficient to compare specific genetic markers — to confirm that parasites recovered from patients across the affected states were genetically related, supporting a single common source.
Taylor Farms de Mexico recalled all iceberg lettuce sourced from central Mexico on July 17. CDC notes that the best-by dates on the recalled product have since passed, meaning it should no longer be available in stores or restaurants, though the agency's investigation into distribution and any secondary contamination remains open.
What comes next
The nine most recently added states — Illinois, Indiana, Kansas, Kentucky, Ohio, Oklahoma, Pennsylvania and West Virginia, among others — reflect how far a single contaminated agricultural product can travel through the food supply chain before a source is pinpointed. CDC has also issued clinician guidance urging health care providers to consider cyclosporiasis in patients with prolonged, unexplained watery diarrhea and to specifically request Cyclospora testing, since it is not part of routine stool panels. The agency says it will continue to update case counts as more illnesses tied to the same genetic strain are identified, even though the contaminated lettuce itself is no longer on the market.
