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  1. FDA Voices: Perspectives From FDA Leadership and Experts

FDA, CDC Develop Robust Strategy to Prevent Illnesses Caused by Cyclospora

FDA, CDC join forces during Cyclospora season to prepare for the potential need to rapidly address intestinal illnesses and prevent a cyclosporiasis outbreak.

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photo montage showing a scientist looking into microscope, a scientist preparing a sample in a Petri dish, a world map, a DNA double helix strand, and a photomicrograph of Cyclospora cayetanensis oocysts in a stool sample with text that reads Cyclospora cayetanensis photomicrograph courtesy of CDC

By Frank Yiannas, Deputy Commissioner for Food Policy and Response, U.S. Food and Drug Administration and Monica Parise, M.D., Director, Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention


The U.S. Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) are collaborating to protect consumers from Cyclospora cayetanensis, a parasite that has caused multistate outbreaks of foodborne illness in recent years. When people eat food contaminated with Cyclospora — mostly fresh produce — or drink contaminated water, they can get an intestinal illness called cyclosporiasis.

Photo of Frank Yiannas
Frank Yiannas

Cyclospora infections have largely surfaced in people who traveled in countries in tropical and subtropical regions where cyclosporiasis commonly occurs. Outbreaks of cyclosporiasis have been reported in the United States since the mid-1990s and have been linked to various types of imported fresh produce, including raspberries, basil, snow peas, mesclun, and cilantro. But last year marked the first Cyclospora was confirmed in domestically grown produce.

The number of reported cases has been rising in recent years, in part because of better diagnostic and detection methods. There were nearly 3,000 reported cases of cyclosporiasis in 2018 alone (including both travel-associated and domestically acquired cases), according to CDC estimates. But it is believed that many more cases may go unreported. In 2018, an outbreak tied to salads sold in a quick-service restaurant chain made more than 500 people sick in 15 states, and another associated with prepackaged vegetable trays made 250 people ill in four states.

The number of reported cases typically rises during the spring and summer, usually in May, June and July. CDC conducts enhanced surveillance for cases of domestically acquired illness during this time. With that in mind, as peak season got underway, the FDA and CDC joined forces in advance to prepare for the potential need to rapidly address illnesses and prevent further cases. So far this year, 23 cases of domestically acquired cyclosporiasis have been reported to CDC in people who became ill since May 1, according to the CDC’s monthly update released June 27.

Joining Forces to Address Contamination

The agencies are working to identify data gaps and research needs so that improved tools can be developed to detect, prevent, and control Cyclospora contamination of food.

Monica Parise, M.D.
Monica Parise, M.D.

Together, the FDA’s Coordinated Outbreak Response and Evaluation Network (CORE) and CDC monitor, prevent, and control foodborne illness. When our ongoing surveillance detects foodborne illnesses attributed to Cyclospora, that collaboration ensures that those illnesses are quickly addressed, any outbreaks are quickly contained, and the source of contamination is rapidly identified and removed from the market to prevent additional illnesses. 

After the 2018 outbreaks, the FDA created a Cyclospora cayetanensis Task Force focused on developing a strategy to reduce the public health burden of foodborne illness caused by Cyclospora. This is a multidisciplinary group in which FDA and CDC representatives work to improve traceback during outbreaks, determine potential contributing factors associated with contamination, and identify knowledge gaps and potential preventive controls to reduce the number of illnesses. 

In early June, representatives of the FDA, CDC, industry and academia participated in a scientific workshop to discuss gaps in detection methods and plans for the development of tools that will help keep this parasite out of pre- and post-harvest foods. The workshop was hosted by the FDA’s Office of Applied Research and Safety Assessment and the Joint Institute for Food Safety and Applied Nutrition, established by the FDA and the University of Maryland.

The FDA and CDC have also provided technical assistance to working groups associated with a panel established by industry after the 2018 outbreaks. On June 5, 2019, the panel released an interim report with information and next steps to pursue related to prevention, response and collaboration.

Science and Surveillance to Protect Consumers

As public health agencies, one of the issues we currently face is that it is very difficult to link cases of cyclosporiasis to each other and to contaminated food products, as we routinely do now for bacterial pathogens such as Listeria and E. coli. However, both the FDA and CDC have developed research protocols to sequence the genome of Cyclospora. The information obtained from this research is being used to develop techniques to enable researchers to identify the genetic differences of the parasite, which may allow us to link cases of cyclosporiasis to each other and will make it easier for public health officials to investigate and prevent cases and outbreaks of Cyclospora infections.

Cyclosporiasis is a nationally notifiable disease, meaning CDC receives frequent and timely reports of cyclosporiasis cases from states and jurisdictions where the disease is reportable. The agency, in close collaboration with state and local public health partners, analyzes each reported case for epidemiologic evidence of linkage to other cases, to facilitate rapid identification and investigation of outbreaks. CDC is working to make reporting easier by improving and expanding web-based reporting options for state and local public health partners. During the cyclosporiasis season, CDC regularly updates its website with information on cases of cyclosporiasis that were acquired in the United States. The FDA and CDC are also improving how they share information with each other, to help facilitate rapid identification and investigation of cyclosporiasis clusters.

Last year, the FDA began using a new method, developed and validated by FDA scientists, to detect Cyclospora in food. This new testing method was an important tool used to identify produce that was positive for Cyclospora during the 2018 outbreak investigations. This is a significant step forward because better detection will lead to better prevention efforts. 

Another way we are working to prevent illness is through surveillance sampling assignments. Using this new testing method, the FDA is currently collecting and testing samples of fresh herbs (cilantro, basil and parsley), that have a history of being linked to cyclosporiasis illnesses. In addition, the agency has  been working to train staff with the California Department of Public Health on the FDA’s testing method, and the state plans to collect and test samples of bagged hearts of romaine lettuce for the presence of Cyclospora. These efforts will help the agencies and other stakeholders assess the rate of Cyclospora contamination in these commodities, as well as help identify common factors among any positive samples.

The agency has also developed a method for detecting Cyclospora in agricultural water. This method, currently being validated by the FDA, will be used to help determine routes of contamination when we identify contaminated produce.

Reaching Out to Stakeholders

The FDA and CDC are committed to educating the grower community regarding best practices that can be used to avoid Cyclospora contamination and what to expect if contamination is linked to a farm’s product; physicians and public health officials on symptoms and diagnostic methods; and consumers about the illness and what steps should be taken if they suspect they have been exposed to Cyclospora.

On farms, unhygienic practices can contaminate water and equipment, and farmers are looking for mitigation strategies. Last fall, the FDA created a webpage with information for farmers and a fact sheet on cyclosporiasis and fresh produce. Given the first detection of Cyclospora in domestic produce last year, the FDA has also stepped up outreach to the domestic industry and state partners to help them understand what to expect should additional incidents of domestic contamination occur. The FDA continues to emphasize the importance of worker health and hygiene controls for produce-related activities. For example, the Produce Safety Rule established by the FDA Food Safety Modernization Act stresses the importance of hygienic practices (including handwashing, and wearing intact and sanitary gloves).
Every year before the start of the U.S. cyclosporiasis season, CDC reminds physicians to consider cyclosporiasis when diagnosing diarrheal illnesses. The degree to which physicians and public health officials test patients and collect samples varies throughout the country. Increased awareness among the medical community regarding cyclosporiasis (for example, time from exposure to initial onset of symptoms, seasonality, symptoms, and current available diagnostic methods) can help to more rapidly identify and address emerging outbreaks.
The FDA has created a webpage that includes information about what restaurants, retailers and consumers need to do to protect against Cyclospora contamination.

The Mission Continues

Together, the FDA and CDC are committed to protecting Americans from Cyclospora and other organisms that can make them sick. Both agencies will continue to use all the tools they have available, from new detection techniques to DNA fingerprinting tools to enforcement tools like import alerts, to prevent cyclosporiasis illnesses in the United States.

Any cases of cyclosporiasis that are reported over the summer will only fuel our efforts to respond quickly and put preventive measures in place to protect consumers.

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