Cyclospora outbreak: Which foods carry the parasite?

While the food-borne cyclospora parasite that can cause “explosive diarrhea” isn’t new, the outbreak in the U.S. has Canadians concerned.

The Public Health Agency of Canada (PHAC) explains cyclosporiasis, the illness caused by the parasite, is a nationally notifiable disease in all provinces and territories, meaning health care providers and labs are required to report to government agencies.

“In the spring and summer, there is usually an increase in cyclospora infections acquired in Canada linked to consuming fresh fruit and vegetables imported to Canada from other countries,” agency spokesperson Mark Johnson said.

What’s happening in Canada?

While there aren’t any cases being investigated in Canada, and no confirmed source of the U.S. outbreak, summer remains peak season for infection. 

PHAC says cyclospora is not commonly found on food and is not in drinking water in Canada, but infections usually increase in the spring and summer, linked to consuming fresh fruit and vegetables imported from other countries.

Which food items bring the highest risk of infection?

The risk of a cyclospora infection may increase if consuming contaminated fresh foods imported from tropical and subtropical areas where the cyclospora parasite is common.

PHAC say foods imported to Canada that have been linked to the cyclospora parasite include: basil, cilantro, raspberries, blackberries, mesclun (spring mix) lettuce, snow and snap peas and prepackaged salad mix.

Where are we most at risk of contracting this parasite? 

Cyclospora can be found worldwide, but is most commonly found in tropical and subtropical areas such as Peru, Cuba, India, Nepal, Mexico, Guatemala, Southeast Asia and the Dominican Republic.

Why it can be tough to prevent infections

“It can be hard to prevent cyclosporiasis,” the PHAC said. “This is because washing produce does not always get rid of the cyclospora parasite that causes the illness.”

Why washing produce ‘doesn’t cut it’

Advice from officials is to continue to wash your fruits and vegetables, but an Ontario food safety expert and University of Guelph professor Keith Warriner said washing produce isn’t always enough to get rid of some pathogens and parasites. 

Warriner said cyclospora is like the majority of microbes in that washing can be limited when it comes to getting rid of it.

Cyclospora has a tough, sticky outer shell, which makes it difficult to wash off produce.

“Sticking to the surface is one aspect but (it) also can be entrapped in crevices and stomata,” he said.

How can we rid produce of cyclospora cayetanensis oocysts? 

“Washing doesn’t cut it but we are working on a method based on hydroxyl-radicals to inactivate parasites like viruses and protozoa,” said Warriner.

The cyclospora cayetanensis oocysts, which are the microscopic, dormant sporelike stage of the cyclospora parasite, are resistant to sanitizers such as bleach. The best defence against them is ensuring irrigation water is not contaminated by human sewage.

If you’re really concerned, Warriner advises you to freeze fruit and vegetables if possible.

Cooking can also reduce your risk. 

Should we worry?

In the past, Warriner said cyclospora was related to travel-related infections.

Over the years, it has become endemic, especially in the southern United States, but not in Canada. Quebec has reported an increase in cases, the majority of which are linked to travel to Mexico.

Warriner cautions that although it’s not endemic to Canada, it matters where the product you’re buying is from.

“We should worry as we import most of our fresh produce into Canada from South and Central America where the parasite is endemic,” he said.

In reporting by CTV News earlier this week, University Health Network infection control director Dr. Susy Hota said that as a specific source hasn’t been identified, it’s possible we could see cases in Canada.

U.S. health officials have identified lettuce as a possible cause, with recent reporting suggesting lettuce used at Taco Bell is linked to the outbreak. 

Late Thursday, July 16, the U.S. Centers for Disease Control and Prevention warned against eating shredded iceberg lettuce from Taco Bell restaurants in various U.S. states including Michigan.

Is this a common parasite in Canada?

Warriner explained cyclospora is not common in Canada and the cases that do occur are typically travel-related and related to food-borne outbreaks linked with imported fresh produce.

Warriner said there’s an outbreak in Canada about once every two to three years, but suspects the frequency will increase due to the spread of endemic populations of cyclospora in North America.

“Previous outbreaks have been linked to basil, cilantro, raspberries and lettuce,” he said.

Warriner said numbers are probably underestimated as new diagnostics to detect infectious cyclospora have recently been developed.

Previously, diagnosis was based purely on symptoms and looking at stool samples under the microscope.

Basil and lettuce 

Warriner said not so long ago the only cyclospora cases were linked to basil from Mexico.

“It was an odd food association but thought to be due to the endemic cyclospora in the Baja region, which is where most basil is produced,” he said. “Since then there have been outbreaks linked to lettuce and soft fruit.”

What is the parasite causing ‘explosive diarrhea?’

The tiny parasite can be found on some fresh produce and causes cyclosporiasis, which can lead to symptoms like sudden, watery diarrhea, cramping and fatigue, according to the CDC.

Multiple U.S. states have reported cyclospora infections. Michigan reported more than 4,000 cases.

Since May 1, the CDC has received reports of 1,645 confirmed domestic cases of cyclosporiasis and is aware of more than 5,100 cases that require further analysis to confirm the illness was acquired in the U.S.

In a July 4 news release, Michigan’s Department of Health and Human Services said previous outbreaks in the U.S. and Canada were linked to bagged salad mixes and kits, fresh cilantro (coriander leaves), fresh basil, raspberries, snow peas and green onions.

No specific produce grower or supplier, or specific produce type has been identified as the source of the state’s current outbreak.

“Cyclospora infects the small intestine (bowel) and usually causes frequent, watery and explosive diarrhea,” the agency said.

Symptoms can take a week to develop

Dr. Neha Vyas, a family medicine physician at the Cleveland Clinic, said the cyclospora parasite has previously been found in berries, bagged salad, pre-cut vegetables and fresh herbs such as basil and cilantro.

While anyone can be at risk of getting sick, people who are immunocompromised are especially vulnerable, Vyas noted in a news release.

Symptoms can take up to a week to develop and can include diarrhea, severe cramping, bloating, nausea and fatigue. In severe cases, a patient may require antibiotics. But in most cases, people will recover at home with rest and water.

“If your symptoms are not getting better, if you feel worse, if you’re unable to keep down any fluid, if you have severe abdominal pain, your fever doesn’t go away, or you’re vomiting, you should seek medical attention,” Vyas said.

Vyas added the best thing people can do to prevent getting sick is to thoroughly wash fruits and vegetables under running water before eating them. You should also wash your hands before and after preparing any food.

Cases in Canada

The PHAC told Metroland Media it’s not investigating any cyclospora outbreaks in Canada as of July 8.

A 2025 research article, published by the National Center for Biotechnology Information, said a study noted 5,337 cases of cyclosporiasis were reported in Canada from 2000 to 2022, using data from the Canadian Notifiable Disease Surveillance System, FoodNet Canada and outbreak investigations.

Adults aged 30 to 59 were “disproportionately affected” by the illness.

Enhanced surveillance data identified international travel, particularly to resorts in Mexico, as a common exposure.

Various fresh produce items were identified as items of interest, but few investigations led to the identification of a specific source of illness.

How does the parasite make you sick?

Cyclosporiasis is an illness of the intestines caused by a parasite called cyclospora. Cyclosporiasis is unlikely to spread directly between people, according to the PHAC.

“This is because the parasite can only infect others once it leaves the body through feces. To be able to spread, the parasite needs to be outside the body for about seven to 15 days.”

What are the symptoms of cyclosporiasis?

PHAC says Canadians who have signs of illness, and have reason to believe they have a cyclospora infection, should contact their health-care provider who can address their specific health concerns, conduct diagnostic testing, and advise a course of treatment if required.

It may take seven to 14 days for symptoms to appear after eating or drinking contaminated food or water.

Symptoms of cyclosporiasis may include:

watery diarrhea (this is the most common symptom)abdominal bloating and gasfatigue (tiredness)stomach crampsloss of appetiteweight lossmild fevernausea

Sometimes, symptoms may go away and then return.

Cyclosporiasis is treated with a prescription antibiotic medication.

The PHAC explains symptoms will probably improve within two to three days after starting on medication.

If left untreated, symptoms may last for a few days up to a few months. Most people have symptoms for six to seven weeks.

Young children, older adults, and those with a weakened immune system are at higher risk for a longer or more severe illness.

What is the latest cyclospora advice for Ontario residents?

Public Health Ontario offers the following tips to reduce the risk of cyclosporiasis:

Wash hands after using sanitary facilities and before preparing or eating food;Fresh fruits, vegetables and herbs should be thoroughly washed and scrubbed under running water before they are consumed;Refrigerate cut, peeled or cooked fruits, vegetables and herbs as soon as possible;Thoroughly cooking or baking fruits, vegetables and herbs will eliminate the risk of infection;Travellers, especially to developing countries or places currently experiencing a cyclosporiasis outbreak, should avoid any fruits and vegetables that cannot be peeled or cooked and should drink water from a safe (treated or boiled) source.

While washing fresh produce may not remove all contamination, PHO said it remains an important food safety practice and can help reduce the risk of exposure to a variety of food-borne pathogens.

Ontario residents should continue to follow general food safety practices and stay informed about any public health notices or food recalls, PHO added.

— With files from Mike Pearson