The source of a diarrhea

The source of a diarrhea-causing outbreak in the U.S. has been found. Now what?

Thousands of cases have surfaced in the U.S., but there are still no related cases in Canada

The source of a diarrhea-causing parasite that has been plaguing Americans across multiple states for weeks has been found, so now what?

On Thursday, the U.S. Centers for Disease Control and Prevention (CDC) confirmed that contaminated lettuce imported from Mexico was served at Taco Bell locations in five states: Indiana, Kentucky, Michigan, Ohio and West Virginia.

The contaminated produce contained cyclospora, which is a microscopic parasite that leads to a sickness called cyclosporiasis. The main symptoms include watery and explosive diarrhea, cramps and nausea. The sickness is not known to be deadly and is usually treated with antibiotics.

The heat-loving parasite infects the bowels and spreads through human waste. In the past, people have been infected by consuming fruits or vegetables that were exposed to feces-contaminated irrigation water.

The outbreak, which started May 1, has led to more than 5,000 confirmed cases and 102 hospitalizations in Michigan alone. The four other states have also reported hundreds of cases.

The CDC says it continues to investigate other outbreaks of the parasite that are unrelated to this outbreak. There are at least 34 states in total reporting cases.

Meanwhile in Canada, the public health agency said in an emailed statement Friday that it's not investigating any cyclospora outbreaks. But it said there may still be cases that arise linked to travel or to consuming produce imported from other countries.

What is cyclospora? A diarrhea-causing parasite

Taylor Farms is a company in Salinas, Calif., that has dozens of food processing plants across North America, including a production facility in Vaughan, Ont. It's known for selling ready-to-eat salad kits.

The company has not responded to a request for comment from CBC News. However, in a statement posted to social media Friday afternoon, Taylor Farms said Taylor Farms de Mexico — its Mexico branch — "is voluntarily removing all iceberg lettuce sourced from central Mexico," based on information from the FDA.

Its post indicates that iceberg lettuce in particular is the culprit behind this outbreak.

"While the FDA traceback is indicating a specific independent farm, which represents less than 1% of the U.S.'s iceberg lettuce supply, as the potential source of the outbreak, we have removed all iceberg lettuce from the region indefinitely," reads part of the statement.

The company added that none of its salads or kits are associated with this outbreak and that none of its kits contain iceberg lettuce.

What Canadians should know about the U.S. parasite outbreak

Should I wash my bagged lettuce?

Since there haven't been any cases related to this outbreak in Canada, experts say it's unlikely there is any contaminated lettuce in the country.

"We would have seen cases," said Lawrence Goodridge, a food safety professor at the University of Guelph in Ontario.

"Lettuce has a very short shelf life, two weeks, maybe three."

If you want to be cautious, experts advise eating produce that is peelable or that can be cooked.

While washing produce doesn't guarantee the parasite will be removed, Emily Jenkins, a professor of veterinary microbiology at the University of Saskatchewan, says there is evidence that how you wash matters.

"The rinsing method with free flowing water is actually the most effective at kind of washing things away," she said.

Explosive diarrhea-causing parasite infects more than 1,000 people in U.S.

She also said it's worth looking at where produce comes from when you buy it.

"Things imported from the U.S. and Mexico are under different regulatory systems than things that are grown at home, so another reason to buy Canadian," she said.

Before and after handling produce, the U.S. Food and Drug Administration (FDA) also recommends washing hands and kitchen countertops or utensils with soap and water. Chlorine-based sanitizers don't kill the parasite and shouldn't be used on produce.

What are officials doing to protect Canadians?

The Canadian Food Inspection Agency (CFIA) told CBC News in a statement earlier this week that its food safety system has "multiple layers of surveillance, testing, regulation and public health oversight" that prevent and detect food-borne hazards, including cyclospora.

And during higher risk periods, such as spring and summer, the CFIA said it "implements enhanced oversight measures."

Those measures can include "targeted import controls, additional import requirements where appropriate, increased sampling and testing activities."

The CFIA said Tuesday it was not considering restrictions on the importation of fresh produce from the U.S. The agency has not yet responded to a request for comment Friday.

A diarrhea-causing parasite has infected more than 1,000 in the U.S. Is it in Canada?

U.S. health authorities say lettuce served at Taco Bell locations is source of diarrhea-causing outbreak

CBC News has reached out to the U.S. FDA on its next steps to contain the outbreak but has not yet heard back.

In Canada, Jenkins said next steps would involve issuing a recall notice. That would prompt grocers to remove the impacted food from their shelves and also instruct consumers to throw out any purchased product.

It's also likely, she said, that the supplier will be asked to destroy all product and that there might be further investigations into how the produce got contaminated in the first place.

"The problem with produce is that there's so many places along the chain where it can get contaminated," she said, adding it can happen anywhere from the growing stage to food handling.

Jennifer La Grassa is a videojournalist at CBC Windsor with a focus on health-care stories. Have a story? Email jennifer.lagrassa@cbc.ca

With files from The Associated Press