Federal health officials declared the largest cyclospora outbreak on record over this week, closing the books on a multistate parasite outbreak tied to contaminated iceberg lettuce that sickened 12,883 people, hospitalized 570 and killed two, both in Michigan.
The Centers for Disease Control and Prevention said Thursday that confirmed illness onsets ran from June 14 through August 17 and spanned 21 states, making it by far the largest documented cyclosporiasis outbreak in US history. Case counts peaked in July at more than 1,000 new infections a day before falling to fewer than two a day by August, tracking closely with the removal of the contaminated product from stores and restaurants.
Traced to a single supplier, cause still unclear
Investigators traced the outbreak to processed iceberg lettuce supplied by Taylor Farms de Mexico. The company recalled all iceberg lettuce sourced from central Mexico on July 17, roughly a day after the Food and Drug Administration and CDC first announced they were investigating the illnesses. Even with the outbreak now formally over, the FDA said it has not pinned down how the lettuce became contaminated with Cyclospora cayetanensis, the microscopic parasite responsible for the illness, and that its investigation into the contamination's root cause continues.
Cyclosporiasis typically causes watery diarrhea, cramping, bloating, nausea and fatigue, with symptoms appearing anywhere from two days to several weeks after exposure. Health officials reiterated standard guidance to wash produce thoroughly under running water and, where possible, cook it to at least 158 degrees Fahrenheit to kill the parasite, though raw lettuce is typically eaten without cooking.
According to an analysis by the food-safety law blog run by attorney Bill Marler, the FDA has separately written to the produce industry outlining steps growers and processors should take to reduce contamination risk in leafy greens going forward.
The Taylor Farms outbreak was the largest but not the only cyclospora cluster this summer. The CDC said it continues to track three additional, smaller outbreaks — the largest of which has reached 231 cases — for which investigators have not yet identified a contamination source, meaning some risk from other suppliers may persist even though the Taylor Farms-linked outbreak has formally ended.
