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Food-borne Illness


Food-borne illness, or food poisoning, occurs when you eat food that is contaminated. Learn about the causes and symptoms of food-borne illness, and how to prevent it.

About food-borne illness

Food-borne illness (or food poisoning) occurs when you eat contaminated food. Food-borne illness is a general term for:

  • Infections caused by micro-organisms such as bacteria, viruses and parasites
  • Poisoning by toxins from bacteria or mould in food
  • Poisoning by chemicals in food
  • More than 200 diseases are transmitted through food. (Institute of Food Technologists Expert Report on Food Safety Issues in the 21st Century, 2002)


The most common symptoms of food-borne illness are:

  • Nausea
  • Vomiting
  • Diarrhea
  • Fever

Symptoms can range from mild (a few stomach cramps) to extremely serious (may cause death).


To reduce the chance of food poisoning, ensure that you handle, cook and store food properly. Follow these four steps when handling food:

  • Clean: Wash hands and surfaces often.
  • Separate: Do not cross-contaminate (e.g., do not use the same cutting board for raw meats and vegetables).
  • Cook: Cook food to proper temperatures.
  • Chill: Refrigerate promptly.

Feeling sick after eating contaminated food

There are times when you might feel sick right after eating bad (contaminated) food. It depends on what caused the symptoms.

  • Food-borne illness caused by bacterial toxins in food or chemical contamination of food usually happens shortly after eating, within 2 - 4 hours.
  • Food-borne infections might take several days to cause illness.
  • Salmonella usually takes 12 - 24 hours, but might take as long as 3 days.
  • E. coli 0157:H7 usually takes 3 - 4 days, but might take up to 8 days to cause symptoms.
  • Food-borne illness caused by the virus hepatitis A usually takes 30 days, but might be as long as 50 days.

Food-borne bacterial infection

Infection occurs when the bacteria in food multiply and cause bowel irritation for anyone who eats the contaminated food. Symptoms usually include fever, abdominal cramps and diarrhea.

Common infections include salmonella poisoning due to undercooked chicken or meat.

Food-borne bacterial intoxication

Intoxication occurs when the bacteria in food multiply and produce harmful poisons or toxins in the food. In some cases, these toxins can be deadly. The main symptom of a food-borne intoxication is usually vomiting, but might also include diarrhea.

A common intoxication is Staphylococcus aureus (e.g., sliced meat and custards left at room temperature). Clostridium botulinum (Botulism) is less common but more severe (e.g., improperly canned products such as vegetables and meats, foil-wrapped potatoes).

Notifying your doctor

If you feel sick and think that you might have a food-borne illness then visit your doctor, who will run tests to determine if you have become ill due to contaminated food.

If you have a food-borne illness:

  • Your doctor will notify the Health Department of positive results.
  • A public health inspector will investigate your case and follow up with you and/or the food premise to find what might have been the source of the contaminated food.