Food Poisoning

Food poisoning results from eating food or drinking water that is contaminated with a virus, bacterium, parasite, or chemical that causes illness. This condition can result when foods have not been properly prepared or stored or when water has not been adequately treated to remove contaminants. Food poisoning can result from eating poisonous plants or animals.

Robin's Story

Robin and her friends squeezed every pleasure they could into the early days of September before school started. The make-your-own-sundae party at Robin's was the best time they had all summer, but a day or two after the party, Robin and her friends were all sick. They all had diarrhea, fever, and stomach cramps, and had vomited more times than they had ever imagined possible. The culprit was Salmonella enteritidis bacteria. Unseen, odorless, and tasteless, the microscopic organisms contaminated ice cream ingredients on the truck ride to the ice cream factory. The reason for this contamination was that the truck had not been cleaned from its previous load—unpasteurized raw eggs, which are a prime breeding ground for Salmonella.

What Is Food Poisoning?

Food poisoning is a serious public health concern in the United States and around the world. The Centers for Disease Control and Prevention (CDC) estimates that there are at least 250 food-borne illnesses. Even though most food poisoning is not severe enough to require treatment by a doctor, food poisoning in the United States costs between $5 and $6 billion annually in direct medical care and lost productivity.

Food poisoning is caused by eating foods contaminated with a harmful virus, bacterium, parasite, or chemical. Organisms that can contaminate food live in the soil, raw meat, raw milk products, and animal feces and on bugs, rodents, unwashed hands, and food-related equipment. The organisms most likely to cause food poisoning are Norovirus, E. coli, Salmonella, Clostridium perfringens, Campylobacter, and Staphylococcus aureus. Food can be contaminated any time that food handling, preparation, or equipment is unsanitary and at any point in the farm–to–table fork cycle. Some common causes of contamination are unrefrigerated, perishable * food; raw or undercooked foods; or preserved foods that were not cooked at high enough temperatures. The CDC estimates that about 97 percent of all food poisoning comes from improper food handling. Of that, 80 percent occurs from food prepared in businesses (e.g., restaurants or cafeterias) or institutions (e.g., schools or jails). The remaining 20 percent occurs from food prepared at home.

* /AIDS * that weaken the immune system are at the highest risk of dying from certain kinds of food poisoning. The elderly are particularly vulnerable to food poisoning for several reasons including decline in immune system functioning associated with aging, decreased production of stomach acids, lack of proper nutrition and physical exercise, and increased use of antibiotic medications. Older people who reside in nursing homes are especially vulnerable to episodes of food poisoning.

Microorganisms responsible for common food-borne illness

Microorganisms responsible for common food-borne illness
Table by GGS Information Services © 2016 Cengage Learning®.

How Does Food Poisoning Occur?

Bacteria are a common cause of food poisoning. A single bacterium that divides every half hour can produce 17 million offspring in 12 hours. Bacteria fall into two general categories. One group causes symptoms of food poisoning by directly infecting the intestines and causing irritation and diarrhea. The other group releases toxins as they grow and reproduce. These toxins affect the digestive system and often cause vomiting and/or diarrhea. Many bacteria cause food poisoning. The following are a few of the more common ones.

A large group of viruses called Norwalk, Norwalk-like, or noroviruses are an extremely common cause of food poisoning. In the early 2000s, Norwalk viruses were often in the news for causing outbreaks of diarrhea and vomiting on cruise ships and in nursing homes. These viruses are usually transferred to food from infected food handlers.

Parasites that cause food poisoning usually come from contaminated water. They often cause mild symptoms that develop slowly but last for several weeks. Giardia and Cryptosporidium are two common waterborne parasites that cause diarrhea.

Natural poisons found in some wild mushrooms can cause various symptoms, including nausea and vomiting, hallucinations, coma * , and death, depending on the amount and species of mushroom eaten. Mushroom poisoning is a medical emergency. Oysters, clams, mollusks, and scallops can contain toxins that affect the nervous system. Individuals often feel tingling in the hands and feet and may become dizzy and have difficulty breathing. Shellfish poisoning is a medical emergency because the muscles needed for breathing may become paralyzed. Certain fish that have not been properly refrigerated or that contain toxins can also cause illness.

Preventing Food Poisoning

Poisoning that results from eating food contaminated by Clostridium botulinum bacteria is called botulism. The word “botulism” is derived from the Latin word “botulus,” which means sausage.

Originally, scientists believed that the botulinum toxin could only be produced in the presence of animal protein, such as meat. But in 1919 a botulism outbreak was traced to canned vegetables from a commercial cannery in Kansas. That same year, another botulism scare involved canned olives. Both incidents prompted stricter regulatory control of food processing technology. Most cases of botulism in the United States in the 20th century occurred from improperly home-canned foods or from a honey containing C. botulinum given to infants.

In the early 2000s, people realized that C. botulinum produces a toxin that affects the nervous system and causes paralysis. If left untreated, botulism is often fatal. With the development of artificial respirators, the fatality rate for treated botulism is around 2 percent in the United States.

What Are the Symptoms of Food Poisoning?

Symptoms of food poisoning can occur in as quickly as one hour and as long as three days after contaminated food is consumed. The symptoms usually begin suddenly. People with food poisoning often have nausea, violent vomiting, frequent diarrhea, painful stomach cramps, and fever. They may also feel dizzy or have blurred vision or difficulty breathing.

How Is Food Poisoning Diagnosed?

Doctors diagnose food poisoning by asking about symptoms, conducting laboratory stool cultures * that test for the presence of specific bacteria in feces, and having food samples analyzed. In mild cases, it usually is not necessary to determine exactly which organism caused the symptoms. In the case of chemical and natural toxins, it is much more important to determine the exact cause of the food poisoning so that specific treatment can be given. Large outbreaks of food-borne illness may be investigated by the local or state department of health or by national organizations such as the CDC.

How Is Food Poisoning Treated?

Food poisoning lasts for one to seven days and usually does not require hospitalization. Hospitalization is necessary for serious cases of certain types of food poisoning or when the diarrhea or vomiting has caused dehydration * * to fight the infection. Some people may be experience relief from over-the-counter or prescription antidiarrheal medications such as loperamide (Imodium), attapulgite (Kaopectate), diphenoxylate and atropine (Lomotil) and/or bismuth subsalicylate (Pepto-Bismol).

Individuals infected with E. coli, Salmonella, or Shigella organisms and who work in day cares, hospitals, restaurants, kitchens, and other locations where food is handled and prepared should not return to work until stool culture samples are negative for these organisms.


Following basic guidelines will help prevent most food poisoning:

Even when individuals keep themselves and their food clean, contamination may have happened earlier in the production process, as with Robin's ice cream. Food processors, growers, and distributors need to take steps to keep food safe with clean processing plants and safe and sanitary storage of food. The U.S. Department of Agriculture, the U.S. Food and Drug Administration (FDA), and local state and city health departments have strict rules for these businesses that are carefully enforced.

Sing Your Way to Clean Hands

One of the ways to be sure your hands are clean is to wash them under warm running water with soap for at least 15 to 20 seconds. That is the length of time it takes to sing the “A-B-C” or “Happy Birthday” songs.

See also Bacterial Infections • Botulism • Diarrhea • Fluid and Electrolyte Disorder • Gastroenteritis • Giardiasis • Intestinal Parasites • Parasitic Diseases: Overview • Shigellosis (Bacillary Dysentery) • Salmonellosis


Books and Articles

McKenna, Maryn. “Food Poisoning's Hidden Legacy.” Scientific American, April 1, 2012. Available online at (accessed March 19, 2016).

Morris, J. Glenn, Jr., and Morris Potter. Foodborne Infections and Intoxications, Fourth Edition. Waltham, MA: Academic Press, 2013.

Rauf, Don. What You Can Do About Food Poisoning. New York: Enslow Publishing, 2015.

Websites . “Food Poisoning.” (accessed March 19, 2016).

MedlinePlus. “Foodborne Illnesses.” U.S. National Library of Medicine, National Institutes of Health. (accessed March 19, 2016).

National Institute of Allergy and Infectious Diseases. “Foodborne Diseases.” (accessed March 19, 2016).

National Institute of Diabetes and Digestive and Kidney Diseases. “Foodborne Illnesses.” (accessed March 19, 2016).


Centers for Disease Control and Prevention. 1600 Clifton Rd., Atlanta, GA 30329-4027. Toll-free: 800-232-4636. Website: (accessed March 19, 2016).

U.S. Food and Drug Administration. 10903 New Hampshire Ave., Silver Spring, MD 20993. Toll-free: 888-463-6332. Website: (accessed March 19, 2016).

* perishable means able to spoil or decay, as in perishable foods.

* HIV, or human immunodeficiency virus (HYOO-mun ih-myoono- dih-FIH-shen-see), is the virus that causes AIDS (acquired immunodeficiency syndrome).

* AIDS, or acquired immunodeficiency (ih-myoo-no-dih- FIH-shensee) syndrome, is an infection that severely weakens the immune system; it is caused by the human immunodeficiency virus (HIV).

* coma (KO-ma) is an unconscious state, like a very deep sleep. A person in a coma cannot be awakened, and cannot move, see, speak, or hear.

* cultures (KUL-churz) are tests in which a sample of fluid or tissue from the body is placed in a dish containing material that supports the growth of certain organisms. Typically, within days, the organisms will grow and can be identified.

* dehydration (dee-hi-DRAY-shun) is a condition in which the body is depleted of water, usually caused by excessive and unreplaced loss of body fluids, such as through sweating, vomiting, or diarrhea.

* antibiotic (an-tie-by-AH-tik) is a drug that kills or slows the growth of bacteria.

Disclaimer:   This information is not a tool for self-diagnosis or a substitute for professional care.

(MLA 8th Edition)