Parasites in the News: Cyclospora and Lettuce
(Note: Background information on Cyclospora comes from the Food and Drug Administration’s Bad Bug Book which is an excellent reference guide)
On July 16, 2026 the FDA announced an investigation into a 5-state outbreak of Cyclospora illnesses linked to certain shredded iceberg lettuce from Mexico served at Taco Bell locations in Indiana, Kentucky, Michigan, Ohio, West Virginia and Oklahoma. According to FDA’s Coordinated Outbreak Response and Evaluation (CORE) table, the agency is currently investigating four other cyclosporiasis outbreaks aside from the nine-state cluster, comprising eight, ten, 18, and 72 cases. A food vehicle of infection has not yet been identified in any of the latter outbreaks.
Another outbreak investigation is ongoing in North Carolina; at this time, there is no apparent link to the 5 state outbreak involving shredded lettuce. 561 cases of cyclosporiasis linked to parsley, cilantro, and other fresh produce have been reported.
The Centers for Disease Control and Prevention said it has received reports of 1,645 confirmed cases of cyclosporiasis since May 1, including 141 patients who were hospitalized. (As of July 24, this number was revised upward to 1,947) The CDC said it is aware of more than 5,100 cases that require further analysis to confirm.
Michigan health officials report 7,664 confirmed cases of cyclosporiasis in the state. Illnesses started on dates ranging from May 13, 2026, to July 13, 2026. There have been 94 hospitalizations, and no deaths have been reported. Interviews with 190 of those cases indicate that 90% of those interviews reported eating shredded iceberg lettuce at Taco Bell. Taco Bell is not the only one affected. Sysco has also stopped distributing lettuce from Taylor Farms.
While the FDA’s traceback (tracing the food from the point of use back to the source) of the food identified Taylor Farms de Mexico of Guanajuato, Mexico as the probable source of the lettuce, as of July 19, there is no supporting laboratory analysis of samples. Product analysis and the investigation are ongoing. Taylor Farms has voluntarily recalled all iceberg lettuce sourced from central Mexico from the U.S. market.
Recall Information: Taylor Fresh Foods’ recall notice included Marketside-brand product available at Walmart: 12 oz and 24 oz Iceberg Salad with Best if Used by dates 7/18/2026 to 8/3/2026; and 8 oz and 16 oz Shredded Lettuce with Best if Used by dates 7/18/2026 to 8/3/2026.
A sample of lettuce from Taylor Farms was reported positive for Cyclospora on July 18, 2026; this analysis was subsequently declared a false positive due to analysis complexity. That sample was not part of the recalled lettuce and the investigation is ongoing.
False Positive Test Explained: A false positive test analysis incorrectly indicates the presence of an organism. This mistake occurs in many types of laboratory test analyses (water, food, blood) for a variety of reasons ; this is why test results are often confirmed with a second analysis.
Cyclospora is a microscopic parasite. Its detection may require specialized laboratory techniques which might misidentify other materials as the parasite. The age and condition of the sample, the laboratory technique preparing the sample and the reaction of the parasite with other organisms – these are all factors affecting proper analysis. Further, the structure (matrix) of the food sample can mask parasites due to high water content, fat, or other microbes. Effective enrichment and concentration steps are needed, but these can introduce contamination risks or degrade fragile parasite stages.
Most foodborne illness investigations, in my 31 years of experience, do not have food samples available for analysis. This is not unusual. Either the ill people do not realize they contracted a foodborne illness or the onset time after eating was lengthy; the food has not been retained or preserved to allow accurate analysis. Interviews with affected people, ill and not ill, and statistical analysis are the conclusive factors which point to the probable cause. Without the sample analysis, however, interviews and statistical analysis must be conclusive. This is no doubt the FDA’s approach, at least until more food samples can be obtained.
So it is no surprise to read this comment from the FDA Commissioner Donald Prater: “False positives are not common,” Prater told reporters on Monday. “Test results are difficult to obtain, and most of the time, our traceback and epidemiologic information are what allows us to determine the source of the outbreak”.
Cyclospora Explained: Cyclosporiasis is caused by a parasite and spreads when infected feces contaminate food or water. Person to person spread is not likely since the parasite must grow in warm temperatures before becoming infective. The illness is more common in warmer temperatures such as are found in the tropics. Some people have no symptoms and carry the organisms in their lower intestines (bowels) for extended time periods, periodically shedding the parasite in fecal material where, after a couple of weeks growth, it may contaminate food or water. Symptoms typically begin about a week after infection and include frequent watery diarrhea, loss of appetite, bloating, nausea and fatigue, lasting from two days to two weeks or longer. The elderly or very young and people with weak immune systems are at higher risk of severe illness than are other people.
Raspberries, lettuce, and other fresh produce imported from areas around the tropics are at higher risk of being contaminated with Cyclospora than is fresh produce from other regions. The illness is not as common in this country but once established in the food supply chain, it can be difficult to isolate and remove. The illness is not spread between people since g
Things to Do: Here are some ideas of what you can do, as a food service operator and as a consumer. They apply to every aspect of food service and will be familiar:
1. Reliable suppliers are always critical; research your choices carefully and insist on food safety documentation (letters of guarantee, evidence of licenses and inspections). Consider multiple suppliers in case of problems;
2. Place your email address on all relevant food safety web sites; this will assure your prompt notification in cases of recalls or safety alerts;
2. During produce washing, throw away the outer two or three layers of produce;
3. Scrub firm produce with a vegetable brush;
4. Thoroughly wash the produce; while this is an important precaution, do not expect it to kill the parasite (so your supplier again is critical to limit any possible contamination);
5. Always wash produce, even when the package says it’s prewashed;
6. Cyclospora is resistant to chlorine based produce rinses and to routine washing;
7. The parasite can be killed by cooking to at least 1580F.;
8. The parasite is not spread person to person but it is spread through feces – wash your hands thoroughly, especially after the bathroom; use disposable gloves during preparation;
9. Carefully clean and sanitize surfaces, utensils and equipment between uses;
10. Monitor employee hygiene carefully (as always), including hand washing and symptoms of illness.
Sources:
FDA Bad Bug Book 2nd Edition
“Bloomberg School ‘We Had It Coming’: Cyclosporiasis Outbreak Reveals Holes in Food Safety System” How gaps in surveillance allowed a hardy foodborne parasite to reach thousands of Americans”. https://publichealth.jhu.edu/2026/understanding-the-cyclosporiasis-outbreak
“Cyclospora” https://www.fda.gov/food/foodborne-pathogens/cyclospora
“Michigan cyclosporiasis outbreak continues to spike, reaching 7,664 cases” CBS News Reports 7 /23/26
“Positive Cyclospora test linked to lettuce was false alarm: FDA” Yahoo!News 7/19/26
“Taylor Farms still tied to cyclospora outbreak despite ‘false positive, FDA says” Politico 7/20/26
“Taylor Farms Lettuce Cyclosporiasis Outbreak Expands to Nine States; CDC Reports Nearly 2,000 Cases, State Counts Exceed 10,000” Food Safety 7/24/26
“Parsley and Cilantro Linked to Cyclospora Outbreak By North Carolina Officials” 7/23/2026 People
Thank you for reading! David