Did you know Listeria can survive on the food in your freezer?

Did you know that unlike other common harmful bacteria,Listeriacan not only survive but thrive in the chilly environment of your freezer?

There havebeen several frozen food recalls in Canada in recent weeks(here,here, here, here, full list here) due to concerns over possible Listeriamonocytogenescontamination.

RickHolley, a University ofManitobafood safety expert, saidthat's one reason why Listeriais far more dangerous than contaminants such as E. colior salmonella.

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"This little organism can grow at refrigerator temperatures, so if there's any moisture at all around on fresh produce, the organism can reach numbers that can cause older folks and people who have immune system malfunctions [to get sick],"Holleysaid.

Fridges can act as incubators for the bacteria, whereasE. coliand salmonella often die off in the cold, Holley said.

The usual threshold that makespeople sick is3,000 or moreListeriabacteria per gram of food,Holleysaid. Left to grow in a fridge,and the number of bacteria can cross the threshold, leavingpregnant women, seniors and those with chronic health issues vulnerable to serious cases of listeriosis.

More lethal than other bacteria

The mortality rate forListeria-borneillnesses is also "unusually high"compared toE.colior salmonella,Holleysaid.

Thebacteria isubiquitous "It's everywhere in very low numbers,"Holley said. It can be found in soil or grass in small quantities thatoften don't pose much of a health risk.

But when it builds up andbecomes concentrated on equipment in food processing plants, "where things are not ideally clean," foods that come into contact with Listeriacan be shipped from one factoryto fridges across the country fairly quickly.

"It can become dominant and be shed into the food," he said."Sometimes, certain areas in some of these plants can build up these bacteria."

That's more or less what happened in 2008, when20people died after aListeriaoutbreak was linked backed to contaminated processed meats from Toronto. Another 36cases ofListeria-relatedillnesses were reported in connection with the outbreak, Health Canada reported.

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While it's resilient enough to stay alive in the cold, the bacteria is usually killed when cooked at "lethal" temperatures at or above 71 C,Holleysaid.

A full list of product recalls is available on the Canadian Food Inspection Agency's website.