A mysterious cluster of E. coli infections across Canada may be linked to leafy green vegetables, says the Public Health Agency of Canada.

The agency has released a public health notice saying it is aware of 12 cases of E.coli in Alberta, Saskatchewan, Ontario and Newfoundland and Labrador that seem to be connected.

All the patients became ill between March 13 and 31, and the E. coli bacteria in each case has the same genetic fingerprint.

So far, federal and provincial public health investigators haven't been able to pinpoint how the cases are connected but they suspect that exposure to leafy greens such as lettuce, kale and spinach might be a cause.

The Canadian Food Inspection Agency has not been able to identify a specific product yet, though their investigation continues.

Leafy green vegetables contaminated with E. coli pose a danger because they generally are not heated to temperatures that would kill off the bacteria.

PHAC is reminding Canadians to follow safe food-handling practices when handling all vegetables to reduce the risk of illness. That means washing fruits and vegetables before eating, wiping down counters, and washing hands and cutting boards with warm soapy water.

E. coli can cause a range of symptoms that appear one to 10 days after contact with the bacteria. Most develop severe stomach cramps, vomiting and diarrhea that is sometimes bloody. Symptoms typically clear up within five to 10 days.

Some people do not get sick at all, though can still spread the infection to others. Others become seriously ill and must be hospitalized. The toxins created by the bacteria can lead to severe dehydration, kidney failure or death. There is no specific treatment other than providing comfort and rehydration.

PHAC offers these tips for preventing E. coli contamination:

  • Keep refrigerators clean and at a temperature below 4 degrees C (40 degrees F). Install a thermometer in your fridge to be sure.
  • Place raw meat, poultry and seafood in containers on the bottom shelf of the refrigerator. Use containers that are large enough to prevent raw juices from dripping onto other food or touching other food.
  • Keep raw food away from other food while shopping, storing, preparing and serving foods.
  • Read labels and follow cooking and storage instructions for all food. When buying food, make sure to check the “best before” date, and if the product has expired, let the store know.
  • Refrigerate or freeze perishable food within two hours of cooking.
  • Freeze or consume leftovers within four days of cooking. Always reheat leftovers until steaming hot before eating.