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What Are the Most Common Causes of Food Poisoning in Canada?

In the wake of a massive E. coli outbreak at several Calgary daycares, many Canadians are wondering how foodborne illnesses occur and what causes food poisoning.

The Public Health Agency of Canada (PHAC) estimates about four million Canadians contract a foodborne illness each year, of those, roughly 11,600 are hospitalized and 238 die.

Of the estimated four million illnesses each year, 1.6 million are caused by known bacteria, viruses or parasites, while 2.4 million cases come from unknown causes.

“They only record a foodborne illness if you go to a hospital or you take a sample and put it to a central lab. If you go to a hospital with diarrhea, they’ll instantly take a sample. So our statistics are very unreliable. And that doesn’t just go for Canada, it goes for most of the world,” Keith Warriner, professor in the Department of Food Science at the University of Guelph, told CTVNews.ca Thursday.

Warriner says people usually contract foodborne illnesses by eating contaminated food.

“A lot of things can cause foodborne illness or food poisoning,” Warriner said. “There’s about 30,000 different types of bacteria we know about and only one per cent of those are actually dangerous to us and animals.”

He says, generally speaking, you can categorize what causes food poisoning by severity.

“Sometimes you’ll eat something, and you say, ‘I feel like I’ve got a 24-hour flu,’ and that could be a virus or basically another pathogen that doesn’t stimulate the immune system so much. Sometimes you can consume pathogens, like listeria, and not show any symptoms at all. But if you’re in a susceptible group—the elderly, immunocompromised, pregnant—then you can suffer a lot. And these can be very severe from simple sickness right through to death.”

Warriner adds those microbes have their own way of “disrupting” your body and causing symptoms including vomiting, fever, diarrhea, aches and pains. You can get sick by eating, handling, and in some cases inhaling pathogens from contaminated food, he says.

“Staphylococcus aureus, for example, can cause sudden death syndrome, you know, by a cut and that can be foodborne or it can be, you know, basic commensal,” Warriner said.



Norovirus is the leading cause of foodborne illnesses and hospitalizations in Canada, according to the PHAC. The virus accounts for an estimated one million illnesses, 1,180 hospitalizations and 21 deaths in the country each year.

“It kind of outweighs all the bacteria, all the parasites we know. So norovirus is the number one. Usually it’s a food handler’s disease, that’s person-to-person, person-to-food,” Warriner said.

PHAC says 65 per cent of known causes of food-borne illnesses in Canada are norovirus.

The main symptoms of norovirus include nausea, diarrhea, stomach pains and cramps and vomiting, according to the PHAC, children usually experience more vomiting than adults.


Clostridium perfringens is a bacteria that makes up an estimated 177,000 illnesses in Canada each year.

“Similar to (norovirus) is Clostridium perfringens, which basically gives you a bout of diarrhea for about a day, and you forgot about it,” Warringen said.

The PHAC says symptoms of Clostridium perfringens illness include diarrhea, pain and cramps, stomach bloating, increased gas, nausea, weight loss, loss of appetite, muscle aches and fatigue.

Symptoms typically last eight to 12 hours, however they can last as long as one to two weeks in the very young or elderly, according to the PHAC. In rare cases, you may become dehydrated and need to be hospitalized.


The PHAC describes E. coli as one of the top foodborne bacteria causing severe illness. The bacteria is responsible for an estimated 12,800 illnesses, 245 hospitalizations and eight deaths annually.

An E. coli outbreak occurred on Sept. 4 at 11 Calgary daycares with 310 lab-confirmed cases of the bacterial infection.

“The reason why we focus on things like E. coli and Listeria, is that numerically, they only cause a few thousand cases a year, but the severity of them is very vast,” Warriner said.

Symptoms of an E. coli infection include nausea, vomiting, headache, mild fever, severe stomach cramps and watery or bloody diarrhea and most of them will end within 10 days of becoming infected, according to the PHAC.

The health agency adds while most people recover on their own, some may have a more serious illness that could hospitalize them, cause long-term health problems or even death.


Listeria monocytogenes is the leading cause of deaths related to foodborne illness each year in Canada, according to the PHAC. It causes an estimated 178 illnesses, 150 hospitalizations and 35 deaths annually.

The health agency says while many people are exposed to the Listeria bacteria, only some get sick with listeriosis, which is the disease that is caused by the bacteria.

Symptoms of listeriosis include fever, nausea, cramps, diarrhea, vomiting, headache, constipation and muscle aches. In severe cases listeria bacteria can spread to your nervous system and cause a stiff neck, confusion, headache and loss of balance.

“So if you’re pregnant, you could lose your baby. If you’re susceptible, you might get septicemia. You might get neurological conditions for over a long time,” Warriner said.


Salmonella infections account for an estimated 88,000 illnesses, 925 hospitalizations and 17 deaths every year, according to the PHAC. The bacteria contributes to one in four hospitalizations of all foodborne illnesses.

“Rarely is (Salmonella) fatal. Usually, if it is fatal, it’s by dehydration,” Warriner said.


Campylobacter is listed as the third leading cause of foodborne illnesses and hospitalizations in Canada, according to the PHAC. It accounts for an estimated 145,000 illnesses, 565 hospitalizations and five deaths per year in the country.

Symptoms of campylobacter bacteria infection include diarrhea (often bloody or watery), abdominal pain, fever, nausea and sometimes vomiting.


To steer clear of eating contaminated food, Warriner says there is a simple rhyme to live by: “When in doubt, throw it out.”

“If you’ve got any doubt—say ‘is this cooked right?’ If you go to a buffet and it’s lukewarm … then you kind of say, ‘well, I don’t want to risk it,'” Warriner said.

He adds avoid cross-contamination by properly cleaning utensils and surfaces before and after use.

Using a meat thermometer is “key” according to Warriner. He says 30 per cent of people own a meat thermometer, while only 14 per cent actually use it. He says he cooks his meat to an internal temperature of 75 C.

He says don’t ever rinse or “wash” chicken because you can spread bacteria around your kitchen more easily. And there’s no need to rinse bagged lettuce either, because there’s a higher chance you’ll contaminate the leafy greens with the germs in your kitchen environment than there is of actually removing anything harmful.

Cleaning is especially important when avoiding harmful bacteria. Warriner says to clean your kitchen using a cup of bleach diluted in a litre or gallon of water, not using vinegar and bicarbonate. He adds putting leftovers in the fridge right away can reduce the chance of pathogens forming on your food, and storing raw and cooked items separately is crucial.

“Put the cooked at the top, raw at the bottom. Don’t put both at the top, and keep it covered if possible,” he said.

Warriner says it’s also important to be prudent when eating out at a restaurant or when ordering food delivery.

“Be wary about when you order food and you receive it. Is it hot? Is it cold? Does it smell right? Does it not? It’s not infallible, you know, because if it was, if we could detect contaminated food, there would be no foodborne illness.”

Source : CTV