What are the most common causes of food poisoning in Canada?

What are the most common types of bacteria, parasites and viruses that cause food poisonings 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.