Two people have died in Canada due to Listeria infections linked to plant-based milks that experts are calling an “unusual” outbreak and are urging caution to prevent further illnesses.

In an update on Wednesday, the Public Health Agency of Canada said a dozen cases have been confirmed, including two deaths and nine hospitalizations.

Of the 12 illnesses that occurred between August 2023 and early July 2024, 10 were reported in Ontario and one each in Quebec and Nova Scotia.

Ontario’s health ministry confirmed to Global News in an emailed statement on Thursday that both the deaths were reported in the province.

Most of the illnesses reported were in adults aged 60 years old or older and in women, PHAC said. Overall, people who have fallen sick in this outbreak are between 37 to 89 years of age.

“More recent illnesses may continue to be reported in the outbreak because there is a period between when a person becomes ill and when the illness is reported to public health officials,” the agency said.

“The unusual thing about this is the plant-based milk source of the infections, because people … think of plant-based milks as kind of a healthy alternative,” said Lori Burrows, professor of biochemistry and biomedical sciences at McMaster University, in an interview with Global News.

The Canadian Food Inspection Agency issued a national recall on July 8 for 18 beverages sold by the brands Silk and Great Value due to potential Listeria contamination.

Almond, oat, coconut and cashew milks are part of the recall, which was triggered by an investigation into a foodborne illness outbreak, the CFIA said.

Canadians are urged not to drink the recalled beverages with expiry dates up to and including Oct. 4.

A food safety investigation is ongoing that may result in additional products being pulled, the CFIA said.

Listeria monocytogenes is a type of bacteria commonly found in soil and it causes foodborne illnesses in humans.

The source of the Listeria contamination in the recalled milks remains unclear and is being investigated by the CFIA.

Lawrence Goodridge, director of the Canadian Research Institute for Food Safety at the University of Guelph, said Listeria can be found everywhere in the soil, but he “can’t recall another time where there was an outbreak linked to plant-based milks.”

In 2008, Canada experienced its worst listeriosis outbreak, with 57 total cases confirmed and 22 deaths traced back to deli meats produced at a Maple Leaf Foods facility in Toronto, Ont.

Burrows said the common denominator is “always the processing plant.”

“These plants are big, they’re moving a lot of food through a lot of different lines either slicing them or in this case, transporting them for packaging through hoses or tubes and all of that has to be decontaminated routinely,” she said.

Milks usually undergo a heat treatment to get rid of potential Listeria or any other bacteria, so it’s likely that there was some of kind breakdown in that process, Goodridge said.

He said it’s also possible that there was some kind of contamination after the heat treatment when the containers were being filled.

Food contaminated with Listeria may not look or smell spoiled but can still make you sick, the CFIA says.

Typical symptoms associated with Listeria illness, called listeriosis, include gastrointestinal problems — like diarrhea, abdominal cramps, constipation, nausea and vomiting — as well as fever, muscle aches.

In severe cases, it can cause neck stiffness, confusion, headache, loss of balance and even death. According to PHAC, symptoms can start as early as three days after eating contaminated food.

But sometimes it can take up to two months for symptoms to show, Burrows said.

Most healthy people will not become sick from Listeria, or it will be a self-limiting infection, experts say.

The risks of Listeria infections are greatest for the elderly, people with weakened immune systems and pregnant women, including their unborn or newborn baby.

Although infected pregnant women may experience only mild, flu-like symptoms, the infection can lead to premature delivery, infection of the newborn or even stillbirth, according to the CFIA.

“This organism can cross the placental barrier and get into the fetus and so it can cause a lot of problems even if the mom doesn’t feel really ill, it can impact the baby,” Burrows explained.

Good sanitation practices can help prevent Listeria infection, experts say.

“If you’re sick, you shouldn’t be preparing food for other people,” Burrows said.

Since plant-based milks have a long life, she also advised checking for any products that people might have stored in their cupboards.

— with files from Global News’ Heidi Petracek