Cyclosporiasis Outbreaks in 2018

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Cyclosporiasis Outbreaks in 2018

Susan Bohm and Katherine Arends, Division of Communicable Disease, MDHHS

cyclospora picture
CDC micrograph of three stained Cyclospora oocysts (red) in a fresh stool sample

For foodborne disease epidemiologists, summertime brings enteric illnesses due to Salmonella, Escherichia coli, and Campylobacter. In recent years, there has been an uptick of foodborne outbreaks caused by the microscopic intestinal parasite, Cyclospora. Cyclospora cayetanensis is the pathogen that causes cyclosporiasis. People become infected by ingesting sporulated oocysts of the parasite. Cyclospora infect the small intestine, causing frequent watery diarrhea, stomach cramping, bloating, nausea, fatigue, loss of appetite, weight loss, and sometimes vomiting, body aches, headache, and fever (CDC, 2018a).  After exposure to a food or water source contaminated with Cyclospora, it takes about 1-2 weeks for symptoms to develop. The illness may last from a few days to one month or longer if untreated. Symptoms may resolve but then reoccur. The infection can be treated with antibiotics. Healthcare providers need to request a specific test to identify Cyclospora in stool samples, otherwise it may not be detected. Cyclosporiasis is common in tropical and subtropical countries and is frequently associated with diarrhea in travelers returning to the US. There is no vaccine for cyclosporiasis and it is possible to become infected more than once with cyclosporiasis. Cyclosporiasis is a reportable disease in Michigan and nationally. 

Past foodborne outbreaks of cyclosporiasis in the United States have been linked to imported fresh produce, such as raspberries, basil, snow peas, mesclun lettuce, and cilantro. This summer, numerous outbreaks caused by Cyclospora have been reported in the United States. As of September 12, 2018, the Centers for Disease Control (CDC) reported there were 2,173 laboratory-confirmed cases of domestically acquired cyclosporiasis in 33 states between May and August (CDC, 2018b).  This number is significantly higher than the number of cases reported for the same period in 2016 and 2017. 

Two large multistate outbreaks of cyclosporiasis were identified this summer by foodborne disease investigators. One outbreak was linked to the consumption of prepackaged vegetable trays, which contained broccoli, cauliflower, and carrots with a dill dip, and were sold at convenience stores in the Midwest. Nationally 250 people from four states were affected; two of these cases were Michigan residents. The supplier of these veggie trays was Del Monte; product associated with this outbreak was pulled from stores and recalled by Del Monte on June 15, 2018. The investigation was unable to identify a single source of contamination for any of the veggie tray ingredients.

The second cyclosporiasis outbreak this summer caused illness in 511 laboratory-confirmed cases from 16 states. Two Michigan residents were cases in this outbreak. Cases reported consuming a variety of salads from McDonald’s restaurants located in the Midwest. McDonald’s stopped selling salads (distributed by Fresh Express) on July 13, 2018, until they found a substitute supplier. The Food and Drug Administration (FDA) detected Cyclospora in a McDonald salad package of romaine lettuce and carrot mix, confirming the salad as the source of contamination; however, the FDA was not able to identify which ingredient was the source of contamination. 

Not all of the cases of cyclosporiasis were explained by these two outbreaks. Smaller clusters of cases implicated basil and cilantro as the contaminants, but for many others the source was not determined. One of the difficulties with cyclosporiasis outbreak investigations is that there are no validated molecular typing tools yet for C cayetanensis, such as what exists for Salmonella or E coli testing. A molecular typing test for C cayetanensis would help to link human cases together with positive food samples. 

Where are these Cyclospora-contaminated produce items coming from? This summer the FDA detected for the first time Cyclospora in domestically grown cilantro as part of their sampling assignment of herbs (FDA, 2018).  While investigating the McDonald’s/Fresh Express salad outbreak, the FDA reported two samples of domestically grown romaine lettuce that were positive for Cyclospora – the second time Cyclospora has been detected in US-grown produce. However, it is important to note that the romaine lettuce samples that were positive for Cyclospora were not from locations associated with the salad outbreak. While surveillance efforts in the past focused on imported produce during cyclosporiasis investigations, these new findings raise concerns of how widespread Cyclospora is in US produce.

What can consumers do to protect themselves from a cyclosporiasis infection (CDC, 2018a)?

  • Wash hands with soap and water before and after handling/preparing fruits and vegetables
  • Fruits and vegetables should be thoroughly washed under running water before eating, cutting, or cooking
  • Cut away any damaged or bruised areas on fruits and vegetables before eating
  • Refrigerate cut, peeled, or cooked fruits and vegetables as soon as possible or within 2 hours
  • People travelling or living in tropical or subtropical countries may be at an increased risk of cyclosporiasis

Recent findings from our national cyclosporiasis investigations help direct the FDA and the CDC to keep our food supply safe.


Reported U.S. cases of laboratory-confirmed, non-travel-associated cyclosporiasis in people with onset of illness during May–August, 2018*.

Reported U.S. cases of laboratory-confirmed, non-travel-associated cyclosporiasis in people with onset of illness during May–August, 2018
*N=2,173. Data are current as of 9/12/18 (1pm EDT). Data are preliminary and subject to change. These cases occurred in people with no history of travel outside of the United States or Canada in the 14 days before onset of illness. Cases that were associated with one of the two large outbreaks (i.e., the convenience store chain or fast food chain) are colored in blue and yellow.


Centers for Disease Control and Prevention [CDC] (2018a). Parasites – Cyclosporiasis (Cyclospora Infection).

Centers for Disease Control and Prevention [CDC] (2018b). Domestically acquired cases of cyclosporiasis – United States, May-August, 2018.

Food and Drug Administration [FDA] (2018). Statement from FDA Commissioner Scott Gottlieb, MD, on the FDA’s ongoing efforts to prevent foodborne outbreaks of Cyclospora.