Food poisoning is an illness caused by the consumption of food or water
contaminated with bacteria and/or their toxins, parasites, viruses, or
chemicals. After a person has eaten these foods, the microorganisms continue to
grow, causing an infection. Foods can also cause illness if they contain a toxin
or poison produced by bacteria growing in food. Food poisoning is a common,
usually mild, but sometimes deadly illness.
The symptoms of food poisoning may resemble other medical conditions or
problems. Symptoms of food poisoning depend on the type of contaminant and the
amount eaten. The symptoms can develop rapidly, within 30 minutes, or slowly,
worsening over days to weeks. Usually food poisoning is not serious, and the
illness runs its course in 24-48 hours.
Some of the common causes of food poisoning include the following:
• Viruses. Account for most food poisoning cases where a specific contaminant is
- Noroviruses. Group of viruses that cause a mild illness. It is the most
common viral cause of adult food poisoning.
- Rotavirus: Causes moderate to severe illness with vomiting followed by
watery diarrhea and fever. It is the most common cause of food poisoning in
infants and children.
- Hepatitis A. Usually causes mild illness. It is transmitted from person to
person by fecal contamination of food.
• Bacteria. Common types:
- Salmonellae and Campylobacter. Found in warm-blooded animals such as
cattle or swine and may be present in raw meat, poultry, eggs, or unpasteurized
- Staphylococcus aureus. Occur normally on human skin and in the nose and
throat. These bacteria are transmitted to food when handled.
- Escherichia coli (E. coli). Found in the intestines of healthy cattle. An
infection is caused by eating undercooked beef or unpasteurized milk, or
- Others. Including Bacillus cereus, Shigella (traveler’s diarrhea),
Clostridium botulinum (botulism), Clostridium perfringens, and Vibrio cholerae.
• Parasites rarely cause food poisoning. The most commons are:
- Giardia (beaver fever). Causes mild illness with watery diarrhea. It is
transmitted by drinking contaminated water.
- Cryptosporidium. May become a long-lasting problem in people with poor
immune systems. It is transmitted by contaminated drinking water.
• Toxic agents are the least common cause of food poisoning.
- Mushroom toxins. Illness can range from mild to deadly depending on the
type of mushroom eaten.
- Pesticides. Toxins are transmitted by eating unwashed fruits or vegetables
contaminated with pesticides.
- Objects, sometimes swallowed by accident, can be harmful for the organism.
Left: X-ray of a 4 years old child, after swallowing
a metallic sphere (bright white spot on the stomach). Right: view of the metallic sphere after the process of digestion. Compared
to a similar sphere, it has turned black