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Canadian Public Health Association

Foodborne illnesses -- what causes food poisoning

  • Bacteria, parasites and viruses are microorganisms that can cause foodborne illnesses ("food poisoning").
  • Symptoms often resemble the stomach flu (stomach cramps, nausea, vomiting, diarrhea, and/or fever).
  • Symptoms can appear soon after eating contaminated food or but sometimes there are no symptoms for a month or ever later.
  • Those most at risk are young children, the elderly, pregnant women and people with weakened immune systems.
  • Many cases of foodborne illness go unreported.
  • Health Canada and the Public Health Agency of Canada estimate that between 11 and 13 million Canadians suffer from illnesses caused by foodborne bacteria every year.
  • Most people fully recover, but foodborne illnesses can result in chronic health problems in up to 3% of cases, including chronic arthritis and kidney failure.

Some Common Causes and Food Sources

Clostridium botulinum (C. botulinum) is a bacteria that exists commonly in nature, which produces a toxin causing botulism.

  • canned low acid foods and aged meats from marine mammals

Campylobacter is bacteria commonly found in the intestines of poultry, cattle, swine, rodents, wild birds and cats and dogs and in untreated water.

  • undercooked poultry, raw milk or non-chlorinated water

Cyclospora is a microscopic parasite that can cause an intestinal infection called cyclosporiasis.

  • food or water contaminated by infected feces

Escherichia coli 0157:H7 (E. coli) is a bacteria found in the intestines of animals such as cattle, pigs, sheep and poultry.

  • undercooked (especially ground) meat and poultry, raw fruits and vegetables in contact with untreated water, unpasteurized milk and raw milk cheeses, unpasteurized apples juices and ciders, and petting zoos.

Listeria monocytogenes (listeria) is a type of bacterium often in food and elsewhere in nature.

  • soil, vegetation, and human/animal feces

Clostridium perfringens (C. perfringens) is a bacteria that forms spores which can survive normal cooking temperatures and grow when cooked food is kept between 4°C (40°F) and 60°C (140°F).

  • high protein or starch-like foods such as cooked beans or gravies and improperly handled leftovers

Salmonella is bacteria found naturally in the intestines of animals, (especially poultry and swine), birds, reptiles, some pets and some humans.

  • raw poultry, raw eggs, unpasteurized milk and eggs, fruits and vegetables if they have been in soil contaminated with animal waste.

Toxoplasma is a microscopic parasite which infects humans if ingested as oocysts or tissue cysts.

  • raw meats, fruits and vegetables from gardens contaminated with cat feces

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