There’s Never Been A Better Time To Buy Canadian Lettuce
Case counts of a nasty food-borne parasitic infection called cyclosporiasis have skyrocketed in the U.S. since May—especially in Michigan, where nearly 4,300 cases have been reported as of July 16. According to the Michigan Department of Health, the state usually only records about 40 to 50 cases of the illness annually.
It’s not just in Michigan, however: Cyclosporiasis has become a multi-state affair. Thirty-four states are currently reporting cases, with the Midwest being hardest hit, according to the CDC.
“It’s the biggest [outbreak] I can think of, and it’s not over yet,” says Dr. Jennifer Ronholm, Canada Research Chair in Agricultural Microbiology at McGill University.
She notes that the United States doesn’t tend to see high numbers of cyclosporiasis—which is more often seen in tropical or subtropical areas.
There may, however, be some light at the end of the tunnel for some of the harder hit areas of the Midwest.
On July 16, the U.S. Centers for Disease Control (CDC) and the Food and Drug Administration (FDA) announced they had identified a link between cyclospora infections in five Midwest states to one supplier of shredded iceberg lettuce used by Taco Bell. The CDC issued a statement advising people not to eat the product at any Taco Bell in Indiana, Kentucky, Michigan, Ohio and West Virginia.
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While the CDC declined to name the supplier, various outlets, including the Washington Post and the New York Times, are reporting the supplier is California-based company Taylor Farms, which also appears to supply grocery stores.
Taco Bell has reportedly removed the lettuce from its supply chain.
The CDC is continuing to investigate other outbreaks of the illness that are unrelated to Taco Bell.
Here’s what you need to know about the outbreak as the investigation evolves—and whether it should influence your grocery choices here in Canada.
What is cyclosporiasis?
Cyclosporiasis is a gastrointestinal infection that’s caused by a microscopic parasite called Cyclospora. You get it when you accidentally ingest food that’s been contaminated by human feces.
Produce that grows close to the ground like lettuce, herbs and berries is often implicated in such outbreaks, says Dr. Michael Libman, Director of the J.D. MacLean Centre for Tropical & Geographic Medicine at McGill University in Montreal, because it grows on the ground and is more likely to get washed over by infected water as a result of contaminated irrigation water.
“The food has to be fairly heavily contaminated, more than what normally happens in our food processing system. The most common reason for this is because irrigation water has been contaminated or there's been a sewage overflow into areas where these things grow,” he explains.
Irrigation water can get contaminated in a few different ways: through flooding, for example, or via a septic tank issue or sewage leak.
What happens if you eat a contaminated food?
Once you’ve ingested the parasite, it starts replicating in your gut. “There’s a seven to 14-day incubation period,” says Ronholm—meaning that symptoms take a week or two to start showing up.
Those symptoms include severe, explosive diarrhea that can last for weeks and even stop and then start again. Nausea, vomiting, abdominal cramps and bloating are other symptoms of the illness. It’s not life-threatening, though its effects can be felt more seriously among kids, the elderly and the immunocompromised. Currently, the CDC says 141 people between the ages of two and 95 have been hospitalized because of the infection.
And once infected, our bodies shed oocysts—the developmental stage of the parasite, which continues to develop after shedding and can eventually become infective—in our feces, which effectively deposits the parasite back into our wastewater.
“It’s cyclical,” says Ronholm. “It replicates in humans and then we put it out in feces.”
Once it’s flushed, however, it’s likely not going to do more.
“In our part of the world, that's generally not a major problem,” says Libman. “Our sanitation system is pretty good at dealing with waste and our wastewater doesn't usually land on our food.”
Treatment is crucial
The unhappy impacts of cyclosporiasis can last upwards of two months if left untreated.
“It’s a parasite but in this case one specific antibiotic called trimethoprim-sulfamethoxazole does work against it,” explains Ronholm, who advises people to seek medical care if they suspect they have it.
“You would want to be treated for this.”
Is Canada seeing cases of the disease?
Canada records about 300 cases a year of cyclosporiasis a year to the Canadian Notifiable Disease Surveillance System, according to the Public Health Agency of Canada, and most often it’s the result of imported foods.
Canada and isn’t seeing anything like the numbers the U.S. is recording, but Libman notes that Quebec has seen a minor bump in recorded cases over the last month or so—a Montreal Gazette report cites 85 cases currently, nearly triple the number from 2025.
“Over the last three weeks or so we have seen a sudden and marked increase in positives among the patient samples being sent to us,” says Libman, whose lab serves hospital labs on the west side of Montreal.
Libman’s not sure what’s behind that bump, and says there could be a few reasons, including the fact that his lab uses tests that are a bit more sensitive than the standard ones. But he says that people may want to consider steering clear of U.S. produce as the investigation of the outbreak continues to unfold.
Ronholm agrees with the wisdom of playing it safe at the grocery store right now as the outbreak is ongoing and emphasizes that, fortunately, it’s a great time of year to buy local Canadian lettuce and berries exclusively.
That doesn’t mean you have to avoid American produce—the Canadian Food Inspection Agency is still allowing the importing of U.S. produce—but you would be wise to cook it for now, says Ronholm. (Cooking produce to an internal temperature of 158F kills the parasite.)
Cooking produce isn’t a bad idea in general, adds Libman.
“Almost every kind of food borne illness is 100 percent preventable with cooking,” he says.
It’s also a good time to tune up your food safety practices overall: wash your produce thoroughly, especially lettuce (with the caveat that washing, while an important practice that cuts the risk of ingesting nasty bacteria or other contaminants, doesn’t really cut it against Cyclospora).
Future concerns about U.S produce?
For Libman, the outbreak may also be a warning signal about various changes to public health funding that have taken place in the U.S. over the past year that could increase the likelihood of these kinds of food-borne illnesses going forward.
Both Libman and Ronholm note that the U.S. scaled back a surveillance program that included cyclospora, which is a notoriously tricky bug to track in the first place, says Ronholm. That lack of surveillance may have made a difficult job more so by cuts to services.
“The CDC that usually does a great job working on these things has been decimated,” says Libman.
In a recent interview with the Washington Post, one former CDC staffer who quit last year said the cuts likely wouldn’t have affected the real-time response to cyclosporiasis in individual states—but may have impacted broader awareness of how the outbreak was growing.
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Flannery Dean is a journalist based in Hamilton, Ont. She has written features on a range of health topics for Chatelaine—from the healthiest time to eat dinner to new cancer screening protocols. Her work also appears in The Narwhal, the Globe and Mail and The Guardian.
