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Food Poisoning

Food Poisoning Definition

Food poisoning is an illness caused by eating or drinking food or water contaminated with viruses, bacteria, toxins, parasites, or chemicals.

Food Poisoning vs Gastroenteritis (Stomach Flu)

Gastroenteritis (stomach flu) is defined as an infection or irritation of the gastrointestinal tract, especially the stomach or intestines. It is a slightly more specific term that can describe a type of food poisoning; however, the term is used most often to describe stomach irritation or inflammation and is used to describe non-food-related stomach irritations.

Food Poisoning Causes

Viruses and bacteria

Viruses are the most frequent cause of food poisoning in the U.S. The next highest causes are bacteria. About 31 viral and bacterial pathogens are responsible for almost 9.4 million diagnosed food poisoning illnesses per year; about 39 million food poisoning cases are unspecified (undiagnosed). Yearly, about 128,000 people are hospitalized and about 3,000 die from all causes of food poisoning.

The most common pathogens that cause food poisoning and the approximate number of people with food poisoning are:

  1. Norovirus - 5,460,000
  2. Salmonella - 1,030,000
  3. Clostridium perfringens - 966,000
  4. Campylobacter - 845,000
  5. Staphylococcus aureus - 241,000

The most common pathogens that caused hospitalizations and the approximate number of hospitalized patients are:

  1. Salmonella - 19,300
  2. Norovirus - 14,600
  3. Campylobacter - 8, 460
  4. Toxoplasma gondii - 4,400
  5. Escherichia coli (E. coli) - 2,140

The most common pathogens that caused deaths and the approximate number of patients that died are:

  1. Salmonella -380
  2. Toxoplasma gondii - 330
  3. Listeria monocytogenes - 260
  4. Norovirus - 150
  5. Campylobacter - 80

Infectious agents comprise the largest category of food poisoning, but as seen from the above top categories, viral infections comprise the bulk of infected patients but are far less likely to cause hospitalizations and deaths than Salmonella bacteria. Because the bulk of "unspecified" causes is probably similar to the makeup of the diagnosed causes, this grouping of viruses and bacteria is considered to be the main causes of food poisoning in the U.S.


There are many toxins that can cause food poisoning. Some are produced by bacteria on or in food and others are produced by plants and animals/fish or other organisms that are ingested. There are many plants and animals/fish that can be poisonous under certain conditions but they are encountered infrequently or under special conditions.

Some general toxin types, various toxins and their sources:

Bacteria Plants Animals/fish/other
enterotoxins Mushroom toxins Scombroid toxin
exotoxins Belladona Ciguatera toxin
cytotoxins Ricin Sasitoxin
Neurotoxins Hemlock Tetrodotoxin

Even though there are many bacterial, plant, and other toxins that can be ingested with food and water, they are usually limited to relatively small outbreaks.


Most parasites are ingested with contaminated food or water. Some of the parasites ingested include:

  • Giardia
  • Amoeba
  • Trichinella
  • Taenia solium


Certain chemicals are considered toxins that can cause food poisoning. Although there are over 80,000 chemicals used in the U.S., only a few have been well studied. While most do not enter into foods, some do and cause food poisoning. An example of such a chemical is mercury, found in drinking water and in fish such as tuna and marlin. Other examples of chemicals that can be toxic if enough contaminates food and water are pesticides, polychlorinated biphenyls, and lead.

The causes of food and water poisoning are numerous. This brief listing of causes should suffice as a framework to begin more detailed studies of food poisoning.

Medically Reviewed by a Doctor on 9/27/2013

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