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Food poisoning comes from eating food or drinking water that is the contaminated with a virus, bacterium, parasite, or chemical that causes illness. It is also called gastroenteritis.


Foodborne illness is a serious public health concern in the United States and around the world. More than 250 foodborne diseases have been identified. Most food poisoning is unpleasant but not severe enough to require professional medical treatment. However, the economic impact of food poisoning is substantial. The United States Centers for Disease Control (CDC) estimates that food poisoning costs the United States between 5 and 6 billion dollars annually in direct medical care and lost productivity.

The organisms and chemicals that cause food poisoning can contaminate food at any point during the production process. Animal products cause the majority of food poisonings. They can become contaminated during slaughter, processing, transport, storage, or preparation. A vegetarian diet, however, does not protect a person from food poisoning. Fruits and vegetables can be contaminated in the fields from animal feces or pesticides, as well as during harvesting, processing, distribution, and storage. The CDC estimates that about 97% of all food poisoning comes from improper food handling.Of that, 80% occurs from food prepared in businesses (e.g. restaurants or work cafeterias) or institutions (e.g. schools or jails). The remaining 20% occurs from food prepared at home. In the twenty-first century, American bioterrorism experts have become increasingly concerned that a disease-causing organism could intentionally be introduced into the food or water supply to cause a mass outbreak of food poisoning illness.


The CDC estimates that about 76 million cases of food poisoning occur in the United States each year. The specific organism causing the disease is identified in only about 14 million cases. Most cases of food poisoning are mild, but about 325,000 individuals are hospitalized for food poisoning each year in the United States, and about 5,000 die. Internationally, food poisoning is about five times more common in developing countries than in the United States and Europe. In underdeveloped countries where contaminated water supplies are common and refrigeration is rare, foodborne illnesses may cause a billion illnesses and 4-6 million deaths each year.

Food poisoning is an equal opportunity illness. It affects people independent of race, age, or gender. However, the very young, the elderly, pregnant women, and people with weakened immune systems (e.g. people with HIV/AIDS, leukemia, transplant patients) are more likely to have severe cases that result hospitalization and life-threatening complications.

Causes and symptoms

Food poisoning can be divided into two basic types: illness caused by infectious organisms and illness caused by chemicals. The infectious organisms (pathogens) that cause food poisoning are bacteria, viruses, and parasites. Chemicals can be either natural toxins (poisons) found in plants (e.g. poisonous mushrooms) and animals (Japanese puffer fish) or they can be man-made chemicals such as pesticides or herbicides.

Symptoms of food poisoning usually develop anywhere within 1-48 hours after eating contaminated food. Symptoms of chemical food poisoning often appear very quickly. The type of symptoms and their severity depend on the cause of the food poisoning, the amount of contaminated food eaten, and the health of the individual. Symptoms usually develop suddenly. Some common symptoms of food poisoning include:

  • nausea followed by forceful vomiting
  • frequent diarrhea. Stools can be extremely watery and may or may not contain blood
  • painful stomach cramps
  • fever
  • headache
  • dizziness
  • blurred vision, difficulty breathing, tingling in hands and feet (chemical food poisoning)

Microorganisms responsible for common food-borne illness

MicroorganismFood-borne illnessSymptomsCommon food sourcesIncubation
Bacillus cereusIntoxicationWatery diarrhea and cramps, or nausea and vomitingCooked product that is left uncovered —milk, meats, vegetables, fish, rice, and starchy foods0.5–15 hours
Campylobacter jejuniInfectionDiarrhea, perhaps accompanied by fever, abdominal pain, nausea, headache, and muscle painRaw chicken, other foods contaminated by raw chicken, unpasteurized milk, untreated water2–5 days
Clostridium botulinumIntoxicationLethargy, weakness, dizziness, double vision, difficulty speaking, swallowing, and/or breathing; paralysis; possible deathInadequately processed, home-canned foods; sausages; seafood products; chopped bottled garlic; honey18–36 hours
Clostridium perfringensInfectionIntense abdominal cramps, diarrheaMeats, meat products, gravy, Tex-Mex type foods, other protein-rich foods8–24 hours
Escherichia coli groupInfectionWatery diarrhea, abdominal cramps, low-grade fever, nausea, malaiseContaminated water, undercooked ground beef, unpasteurized apple juice and cider, raw milk, alfalfa sprouts, cut melons12–72 hours
Listeria MonocytogenesInfectionNausea, vomiting, diarrhea; may progress to headache, confusion, loss of balance and convulsions; may cause spontaneous abortionReady-to-eat foods contaminated with bacteria, including raw milk, cheeses, ice cream, raw vegetables, fermented raw sausages, raw and cooked poultry, raw meats, and raw and smoked fishUnknown; may range from a few days to 3 weeks
Salmonella speciesInfectionAbdominal cramps, diarrhea, fever, headacheFoods of animal origin; other foods contaminated through contact with feces, raw animal products, or infected food handlers. Poultry, eggs, raw milk, meats are frequently contaminated12–72 hours
ShigellaInfectionFever, abdominal pain and cramps, diarrheaFecally contaminated foods12–48 hours
Staphylococcus aureusIntoxicationNausea, vomiting, abdominal crampingFoods contaminated by improper handling and holding temperatures—meats and meat products, poultry and egg products, protein-based salads, sandwich fillings, cream-based bakery products1–12 hours
Hepatitis AInfectionJaundice, fatigue, abdominal pain, anorexia, intermittent nausea, diarrheaRaw or undercooked molluscan shellfish or foods prepared by infected handlers15–50 days
Norwalk-type virusesInfectionNausea, vomiting, diarrhea, abdominal crampsShellfish grown in fecally contaminated water; water and foods that have come into contact with contaminated water12–48 hours
Giardia lambliaInfectionDiarrhea, abdominal cramps, nauseaWater and foods that have come into contact with contaminated water1–2 weeks
Trichinella spiralisInfectionNausea, diarrhea, vomiting, fatigue, fever, abdominal crampsRaw and undercooked pork and wild game products1–2 days

(Illustration by GGS Information Services/Thomson Gale.)

Contamination that causes food poisoning can occur at every level of the food production process Some examples follow.

  • Growers: application of illegal pesticides and herbicides or their application higher than approved concentrations. In the United States, pesticides use is regulated by the United States Department of Agriculture (USDA) and the Environmental Protection Agency (EPA)
  • Processors: use of contaminated water in processing, inadequate disinfecting of processing equipment, inadequate time and temperature in processing canned or cooked foods, contamination with poisons used to control factory pests, and improper handling of raw materials. In the United States, meatpacking plants are inspected by the USDA, and other food processing plants are inspected by the United States Food and Drug Administration (FDA)
  • Storage and transportation: holding fresh or frozen foods at improper temperatures, inappropriate use of fumigants in warehouses or trucks, inadequate sanitizing of food-carrying tanker trucks (e.g. milk, corn syrup), and contamination by insects or rodent droppings in storage areas
  • Retail outlets and restaurants: food kept at improper temperatures, cross-contamination between raw and cooked food, improper disinfecting of food preparation surfaces, transmission by infected food handlers,


Pathogen—An organism that causes a disease.

Toxin—A general term for something that harms or poisons the body.

and failure of food handlers to wash their hands. Restaurants are inspected by local health authorities.

  • Home preparation: letting food sit out too long at room temperature, inadequate cooking, cross-contamination between cooked and raw food, failure to properly reheat leftovers


Bacterial contamination is the leading cause of food poisoning. At room temperature, bacteria reproduce at astounding rates. 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 causing irritation and diarrhea. The other group release toxins (poisons) as they grow and reproduce. These toxins affect the digestive system and often cause vomiting first followed by diarrhea. Many bacteria cause food poisoning. A few of the more common ones are described below.

Bacteria of the genus Salmonella are common in reptiles, birds, and mammals. They are found most often in eggs, poultry, dairy products, and beef. Infection with Salmonella causes nausea, vomiting, stomach cramps, headache, and low-grade fever. Symptoms begin anywhere from 6 to 48 hours after exposure and may last for 7 days. In people with weakened immune systems, Salmonella

Bacteria of the genus Campylobacter cause more diarrhea illnesses worldwide than any other group of bacteria. They produce fairly mild diarrhea, fever, and stomach cramps. Campylobacter bacteria are found in almost all raw chicken and turkey. Cross-contamination, that is putting cooked food down where raw food had been, is a leading cause of food poisoning from Campylobacter These bacteria are also transmitted by water contaminated with animal feces.

Escherichia coli are a large group of bacteria, only some of which cause food poisoning. E. coli food poisoning usually begins with watery diarrhea that later turns bloody. One strain of E. coli known as 0157:H7 is most often found in undercooked hamburger, but has also been found in ready-to-eat raw spinach. This particular strain can cause kidney failure and death, especially in children and the elderly.

Clostridium botulinium is a bacteria that causes the disease botulism. C. botulinium produces a toxin that affects the nervous system and can cause difficulty breathing and paralysis. Symptoms do not appear until 1 to 4 days after exposure. Botulism is associated with improperly canned food, smoked fish, and honey. Infection with C. botulinium is serious and often fatal.


A large group of viruses called Norwalk or Nor-walk-like viruses are an extremely common cause of foodborne illness. In the mid-2000s, Norwalk viruses were often in the news for causing outbreaks of gastrointestinal disease on cruise ships and in nursing homes. They cause more vomiting than diarrhea than any other viruses. Unlike many of the other causes of food poisoning, these viruses are not usually naturally present in food. They are usually transferred from the hands of infected food handlers to the food that they are preparing, especially to foods such as salads and sandwiches.


Parasites that cause food poisoning usually come from contaminated water. They often cause mild symptoms that are slow to develop but last for several weeks. Giardia causes watery diarrhea and is often acquired by drinking untreated water from lakes or streams. Cyrptosporidium is a parasite that causes large amounts of watery diarrhea for 3–4 days. Healthy people usually recover quickly, but in people with weakened immune systems, symptoms can persist for a long time.

Natural toxins

Natural poisons found in some wild mushrooms can cause anything from nausea and vomiting to hallucinations, coma, and death, depending on the amount and species of mushroom eaten. Mushroom poisoning is a medical emergency. People who believe they have eaten a poisonous mushroom should, if possible, take a sample of the mushroom or their vomit to the emergency room with them. Identifying the type of mushroom causing the illness can help determine the most effective treatment.

Manmade toxins

Manmade toxins include all pesticides, fertilizers, disinfectants, and any other chemicals remaining in food when it is eaten that can cause illness. Contamination is accidental, and often the result of ignorance or a misunderstanding of how to apply the chemical. Symptoms may develop rapidly or slowly depending on the type of chemical and the amount of exposure. Chemical poisoning requires prompt medical evaluation.


Food poisoning is caused by many different organisms, but identifying the exact organism is not usually necessary. Most mild food poisoning is diagnosed by the symptoms of vomiting, diarrhea, and stomach cramps coupled with information about that the individual has recently eaten. The length of time between eating the suspect food and the start of symptoms gives physicians a clue about what particular organism may be causing the food poisoning. Blood and urine tests may be ordered to determine the individual’s degree of dehydration and electrolyte (chemical) imbalances. In most cases, determining the exact pathogen that is causing the food poisoning is relatively unimportant, as treatment tends to be the similar for most causes. However, if diarrhea is persistent, a stool culture may be done to provide more specific information.

When chemical or natural toxin poisoning is suspected, determining the exact cause is more important, and treatment is specific to the cause. The stomach may be pumped and the contents tested. Extensive blood tests are usually needed. Sometimes activated charcoal is used to help absorb the poison in the stomach.


The main goal of treatment for food poisoning is to keep the individual from becoming dehydrated. A loss of 20% of a person’s body fluid is fatal, and 10-15% is serious. In food poisoning, huge amounts of both water and electrolytes can be lost quite rapidly. Vomiting and diarrhea in infants and young children require especially prompt professional treatment because small children can become dehydrated within hours.

Mild cases of food poisoning can usually be treated at home, especially if they are not accompanied by a fever. Dehydration in infants and children can be prevented or treated by giving them oral rehydration solutions such as Pedialyte, Infalyte, Naturalyte, Ora-lyte, or Rehydralyte. These are available in supermarkets and pharmacies without a prescription. Oral rehydration solutions have the proper balance of salts and sugars to restore fluid and electrolyte balance. They can be given to young children in small sips as soon as vomiting and diarrhea start. Children may continue to vomit and have diarrhea, but some of the fluid will be absorbed. In the past, parents were told to withhold solid food from children who had diarrhea. New research indicates that it is better for children should to be allowed to eat solid food should they want it, even though diarrhea continues.

Older children and adults who are dehydrated can be given oral rehydration solutions or sports drinks such as Gatorade. Adults and older children with food poisoning should avoid drinking coffee, tea, and soft drinks, especially soft drinks that contain caffeine, as these liquids promote dehydration. Over-the counter medications to stop or slow diarrhea such as Kaopectate, Pepto-Bismol, or Imodium will not shorten the duration of the disease, but may give the individual some control over his or her bowels. Consult a physician before giving these over-the-counter medicines to children.

Individuals of all ages who are seriously dehydrated need to be treated promptly by a medical professional. In the case of severe dehydration, the individual may be hospitalized and fluids given intravenously (IV; directly into the vein). Drugs may also be prescribed to stop persistent vomiting. Although bacteria cause many cases of food poisoning, antibiotics are not routinely used in treatment. Some studies have shown that antibiotics are necessary only in about 10% of cases.

Individuals who think their food poisoning symptoms are caused by chemicals or natural toxins should seek emergency medical care immediately. These types of food poisoning are too serious to try to treat at home.

Nutrition/Dietetic concerns

Certain foods are more commonly associated with food poisoning than others. These include:.

  • raw and undercooked meat, especially ground meat
  • raw or undercooked poultry
  • raw or undercooked eggs and egg products such as mayonnaise or raw cookie dough. Estimates are that 1 of every 20,000 eggs is contaminated with Salmonella
  • unpasteurized milk products or unpasteurized fruit juice
  • raw shellfish, especially oysters, clams, scallops, and mussels
  • ready-to-eat raw fruits and vegetables
  • wild mushrooms. Note: many mushrooms that are poisonous in North America look almost identical to safe-to-eat mushrooms found in Europe
  • improperly prepared fish such as barracuda or Japanese puffer fish
  • improperly canned foods (homemade or commercial). Note: any can that is leaking or bulging should be discarded
  • soft cheeses such as brie or feta
  • lunch meats or deli meats

Although the food in the United States is very safe, occasionally major outbreaks of food poisoning occur that can be traced to a breakdown in the food handling system. Larger outbreaks can be identified and traced to their source because each state has a list of diseases that health professionals are required to report to the county public health service once positive diagnosis is made. Most states require that doctors and hospitals report confirmed cases of disease caused by Salmonella and E. coli 0157:H7 and several other food poisoning pathogens. This information is then passed on to the CDC.

Most food poisoning occurs to single individual or to a small group of people, such as a family at a picnic. A major food poisoning outbreak is suspected when many people develop the same symptoms of food poisoning within a short time or within the same geographic area. A major outbreak sets off a full investigation by a team of microbiologists, food scientists, process engineers, specialists in food sanitation, and others. In a larger outbreak, the CDC usually coordinates the investigation. The CDC has established a special system called FoodNet to monitor food poisoning reports and look for patterns that suggest an outbreak. Information on chemical and natural toxin poisonings is also collected by the American Association of Poison Control Centers.


Most people have unpleasant gastrointestinal symptoms—vomiting and diarrhea—for a few days and then recover fully from food poisoning. In young children, dehydration is always a cause for concern. Worldwide, dehydration from diarrhea is the biggest killer of children under age 5. If dehydration can be controlled in young children with food poisoning, most recover with few complications. However, E. coli 0157:H7 can cause fatal renal failure in 3-5% of children. This bacteria is most often acquired by eating unpasteurized apple cider or apple juice, alfalfa or bean sprouts.

More serious long-term health problems often result from chemical poisonings. Toxins found in some wild mushrooms and some fish can cause permanent liver damage requiring a liver transplant or death. Pesticides and other chemical contamination can cause liver damage, kidney failure, and nervous system complications. In 2007, apparent chemical contamination of pet food caused the death of hundreds of dogs and cats in the United States.


Appropriate food handling procedures at every level of the production process can go a long way in preventing food poisoning. Growers should apply only approved pesticides and herbicides at levels recommended by the Environmental Protection Agency and the Department of Agriculture. Processors must use clean sources of water to wash produce. Processing machinery must be disinfected regularly, and pesticides used in processing plants must be safe for use around food. In restaurants, food must not be held under warming lights of on buffet tables for long periods.

At home, individuals can help prevent food poison by following these guidelines.

  • Wash hands, food preparation surfaces, and utensils often when handling food
  • Prevent cross-contamination of raw and cooked food. Do not put cooked food back on the same plate or surface that held it when it was raw
  • Cook foods to internal temperatures between 140°F and 180°F (60-83° C)
  • Refrigerate or freeze fresh foods and leftovers promptly
  • Defrost food in the refrigerator or microwave and not on the counter at room temperature. Cook promptly when defrosted
  • Keep food at temperatures above 140°F (60°C) or below 40°F (4° C)
  • Throw out food that has sat at room temperature for 2 hours or more


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