The announcement by health officials prompted the food company to heighten its recall of meat products. Maple Leaf also issued a public apology for the outbreak.
The bacterium is often found in herd animals, meats, unpasteurized milk and unprocessed cheese products. Last Tuesday, a national recall was issued for Maple Leaf products such as sliced corned beef, roast beef, pepperoni, salami, sausages, smoked ham, and turkey.
A complete list of suspected contaminated products is available at the Canadian Food Inspection Agency Web site.
Canadian food and health authorities confirmed that the four deaths and 21 non-fatal listeriosis cases in four provinces are linked to Maple Leaf products produced in a processing plant in Bartor Road. Thirty other cases are still under investigation.
Maple Leaf, one of Canada's largest food processors, supplies its products to food service institutions, restaurants, hospitals and nursing homes.
The illness is most dangerous among old people, pregnant women and people with weak immune systems. Antibiotics are used for its treatment.
Symptoms include fever, muscle aches, nausea and diarrhea. It may spread to the nervous system and can result in headache, stiff neck, confusion, loss of balance or convulsions.
