US federal health officials reported today that 2,173 laboratory-confirmed cases of cyclosporiasis were reported by 33 states in people who became ill during May–August without a history of international travel during the 14-day period before illness onset.

Cyclospora oocysts
Oocysts of C. cayetanensis viewed under differential interference contrast (DIC) microscopy.
Image/CDC DPDx

At least 150 people were hospitalized; no deaths were reported.

The Food and Drug Administration (FDA) says although this case count represents a significant increase from our previous experience with this parasite over the last several years, some of this increase is likely the result of improved public health monitoring for human illness, including better diagnostic tests-namely, increased use of a multiplex molecular assay to examine stool specimens.

Many of this year’s illnesses with Cyclospora are linked to two very large produce-associated outbreaks that we announced over the last several months. One of these outbreaks occurred in the spring. It resulted in 250 illnesses in four states and was linked to Del Monte vegetable trays containing broccoli, cauliflower, and carrots that were sold mostly in convenience stores in the Upper Midwest.

The second outbreak occurred this summer when 511 Cyclospora illnesses were reported by 16 states. Most of these illnesses occurred in the Midwest. This outbreak was linked to McDonald’s salads sold in 14 states in the Midwest that contained a romaine lettuce and carrot mix supplied by Fresh Express.

Although these two outbreaks are large, together they account for less than half (Approximately 35%) of all domestically-acquired Cyclospora cases reported to CDC in 2018.  As noted by CDC, smaller clusters of illness have also been identified and investigations to date have found them to be epidemiologically linked to consumption of basil and cilantro in Mexican-style restaurants. These clusters are similar to clusters of Cyclospora seen in previous years that were traced to imported herbs although our investigation into the source of the current illnesses is ongoing.