Cyclospora outbreak linked to salad mix, cilantro

October 24, 2013

The U.S. Centers for Disease Control & Prevention (CDC) have linked the Cyclospora outbreak that sickened 643 people from 25 states this summer to fresh cilantro from Puebla, Mexico. Most of the people affected became sick between mid-June through mid-July. No deaths have been reported.

Epidemiologic and traceback investigations conducted by state and local public health and regulatory officials in Texas, the Food and Drug Administration (FDA), and CDC indicate that some illnesses among Texas residents were linked to the cilantro. Investigating “clusters of illnesses” can provide critical clues about the source of an outbreak. A cluster of illnesses is defined as more than one unrelated ill person (i.e., they do not know or live with each other) who report eating at the same restaurant location, attending a common event, or shopping at the same location of a grocery store before becoming ill. Investigators identified more than 70 clusters of illnesses in Texas. Most of the clusters identified in Texas involved two or three ill persons.

During interviews with ill persons in Texas, about 50% reported having eaten fresh cilantro 2–14 days before they became ill. This proportion was significantly higher than that reported among ill persons in Iowa and Nebraska (reported by about 10%), and significantly higher than results from a previously conducted survey of healthy persons in New Mexico where 27% reported eating fresh cilantro in the seven days before they were interviewed.

Epidemiologic and traceback investigations were conducted at three restaurants and one grocery store location in Texas, where multiple unrelated ill persons reported having eaten or shopped.

Thirty ill persons reported eating at a single Mexican-style restaurant in Fort Bend County, Texas, in the 2–14 days before onset of illness. Twenty-two ill persons had laboratory-confirmed Cyclospora infection (confirmed cases) and eight were probable case-patients (case symptoms but no laboratory confirmation). An analytic epidemiologic study was conducted that compared foods eaten at the restaurant by 25 of the persons who became ill versus 65 healthy persons who remained well. Ingredient-level analyses were conducted using meal consumption data and recipes. Four fresh produce ingredients were significantly associated with illness: cilantro, whole onions, garlic, and tomatoes. Since these ingredients were served together in many different dishes, such as salsa, the statistical analysis could not definitively identify which of these ingredients was independently associated with illness. However, fresh cilantro was the only ingredient consumed by all 25 ill persons in this study. In addition, salsa containing fresh raw (uncooked) cilantro was associated with illness, while salsa containing cooked cilantro was not.

Consumption of lettuce was not associated with illness in this analysis, and traceback information indicated that lettuce served in this restaurant was not from Taylor Farms de Mexico. Neither red cabbage nor carrots (components of the Taylor Farms de Mexico salad mix linked with illness in Iowa and Nebraska) were used in this restaurant.

The findings in the investigations suggest that there was more than one outbreak of cyclosporiasis during June–August 2013 in the United States. Restaurant-associated illnesses in Iowa and Nebraska were linked to salad mix from Taylor Farms de Mexico in Guanajuato, Mexico. Some illnesses in Texas were linked to fresh cilantro from Puebla, Mexico.

Press release