food poisoning, acute illness following the eating of foods contaminated by bacteria, bacterial toxins, natural poisons, or harmful chemical substances. It was once customary to classify all such illnesses as "ptomaine poisoning," but it was later discovered that ptomaines, the products of decayed protein, do not cause illness. The symptoms, in varying degree and combination, include abdominal pain, vomiting, diarrhea, headache, and prostration; more serious cases can result in permanent disability or death.

Bacterial Food Poisoning

In general, the bacteria that cause food poisoning do not affect the appearance, aroma, or flavor of food. The most common bacterial causes of food poisoning are Salmonella (see salmonellosis), staphylococcus, Escherichia coli, Listeria monocytogenes, Shigella, and Campylobacter jejuni. The symptoms may be caused by toxins produced by the bacteria. The most serious type of food poisoning caused by bacterial toxins is botulism, which results from toxins made by the bacterium Clostridium botulinum.

Salmonella, most notoriously spread via raw eggs, develops from 6 to 72 hours after exposure. Symptoms include severe diarrhea, fever and chills, vomiting, and abdominal cramps and usually last from three to five days. Staphylococcal food poisoning is actually caused by the potent toxins that they produce. Typical sources are unrefrigerated ham, poultry, potato or egg salad, and custards. Carriers and food handlers with staphylococcal skin infections are mainly responsible for the spread of staphylococcus toxin poisoning. The onset of symptoms from such poisoning (similar to those of Salmonella infection) occurs abruptly one to six hours after ingestion of the polluted food. The illness lasts from 24 to 48 hours; fatalities are rare.

Infection with a particular strain of the usually harmless E. coli began to appear in food poisoning cases from the 1980s on, typically in raw or undercooked ground meat. Onset of symptoms comes one to eight days after eating the contaminated food. Symptoms include bloody diarrhea, nausea, and sporadic vomiting, with or without fever. It can progress to kidney failure and death, especially in children.

Listeriosis, caused by the bacterium Listeria monocytogenes, is spread in soft cheeses, undercooked meats, and prepared foods from delicatessen counters. Its onset is abrupt. Symptoms vary with the person's immune status and may include fever, muscle aches, fatigue, and nausea. The illness is especially serious for the very young or for pregnant women, who may miscarry or transmit blood infections or meningitis to the baby. In adults, the disease can progress to central nervous system complications, endocarditis, or pneumonia, and is an especially serious threat to the elderly.

Shigella is spread by contaminated food or from person to person (principally via a fecal-oral route). New strains of bacteria of the genus Shigella have been associated with food poisoning from ground meat. Symptoms include watery diarrhea, abdominal cramps, and bloody mucus in the stools.

Campylobacter enteritis is caused by either of two species of the Campylobacter bacterium. The bacterium is ubiquitous in uncooked poultry. Symptoms (diarrhea, fever, chills, headache) arise 2 to 11 days after exposure and last one to two weeks. Although usually mild, the infection can cause Guillain-Barré syndrome, a weakness of the peripheral nerves that can lead to paralysis and death.

Treatment for most bacterial food poisoning includes rest, sedation, and replacement of fluid loss if necessary. Antibiotics usually are used only in severe cases. Preventive measures in the home include thorough cooking and prompt refrigeration of meats and eggs, washing and peeling fruits and vegetables (and avoiding uncooked produce entirely if a person has a compromised immune system), washing of cooking surfaces and utensils that may have been contaminated by uncooked foods, and careful handwashing after use of the toilet.

Since the 1970s the number of food poisoning cases in the United States has gradually increased, and beginning in the 1980s more virulent organisms and more serious cases of food poisoning with complications leading to miscarriage, kidney failure, or death were observed. Some experts have attributed this to overprescription of antibiotics and the routine use of antibiotics as growth enhancers and to treat disease in livestock, practices that encourage the development of drug-resistant bacterial variants. An increase in the consumption of uncooked fresh produce has also contributed to the increase in food-borne illnesses. The increase in the number and severity of food poisoning cases have led to concern about food inspection and preparation methods, and to consideration of irradiating high-risk foods to eliminate bacterial contamination. More stringent meat inspection procedures were put in place by the U.S. Dept. of Agriculture in 1996 in response to some of these concerns, and the Food and Drug Administration approved the irradiation of meat. The vast majority of food poisoning cases, however, involve fruits and vegetables, seafood, cheese, and products, such as juices or deli salads, made with them.

Food Poisoning by Natural Poisons and Metals

Nonbacterial food poisoning may occur after eating foods that contain a naturally occurring or acquired deleterious substance. Ingestion of poisonous mushrooms or toadstools (see mushroom poisoning) may be followed in a matter of several minutes to two hours by severe thirst, abdominal cramps, diarrhea, vomiting, sweating, dizziness, confusion, collapse, coma, and, occasionally, convulsions. Poisoning may occur also after the ingestion of immature or sprouting potatoes because of the presence of solanine, an alkaloid. Mussels and clams that have fed on poisonous plankton also are a cause of food poisoning, since the poisonous substance is not destroyed by cooking. Ergot poisoning, caused by ingestion of rye grain infected with that fungus, causes damage to the blood vessels and gangrene, as well as gastrointestinal and neurologic symptoms.

It is also possible to take into the body poisons such as arsenic, lead, or mercury via foods that have been accidentally contaminated or sprayed with preservatives and not properly cleansed before ingestion. Food stored in containers lined with cadmium has been known to cause poisoning. Typical symptoms of this sort of food poisoning (diarrhea, vomiting) may occur right away; the nervous system and respiratory systems may be affected with continued exposure.

Definition

Food poisoning refers to illness arising from eating contaminated food. Food may be contaminated by bacteria, viruses, environmental toxins, or toxins present within the food itself, such as the poisons in some mushrooms or seafood. Symptoms of food poisoning are usually gastrointestinal, such as nausea, abdominal pain, vomiting, and/or diarrhea. Some food-borne toxins can affect the nervous system. Food poisoning is sometimes called bacterial gastroenteritis or infectious diarrhea and is sometimes incorrectly called ptomaine poisoning.

Description

Every year millions of people of all ages suffer from bouts of vomiting and diarrhea blamed correctly on something they ate. According to the Centers for Disease Control and Prevention (CDC), up to 33 million cases of food poisoning are reported in the United States each year. Many cases are mild and pass so rapidly that they are never diagnosed. Occasionally a severe outbreak affects many people at once, creating a newsworthy public health hazard. Although the food supply in the United States is probably one of the safest in the world, anyone can get food poisoning. Outbreaks have occurred in schools and colleges (up to 25 incidents reported annually in the United States), among restaurant clientele, in institutions such as long-term care facilities, and in other settings serving the public. Serious outbreaks are rare. When they occur, the very young, the very old, and those with weakened immune systems are subject to the most severe and life-threatening cases.

A variety of bacteria cause food poisoning, including Salmonella, Staphylococcus aureus, Campylobacter jejuni, Escherichia coli, Shigella, and Clostridium botulinum. Each type of bacteria has a different incubation period and duration, and all except the botulinum toxin cause inflammation of the intestines and diarrhea. Food and water can also be contaminated by viruses such as the Norwalk and hepatitis viruses. Environmental toxins (heavy metals) in foods or water, and poisonous substances in certain foods such mushrooms and shellfish are other causes of food poisoning.

Careless food handling between farm and table may create conditions for the growth of bacteria. Vegetables eaten raw, such as lettuce, may be contaminated by bacteria in soil, water, and dust during washing and packing. Home canned and commercially canned food may be improperly processed at too low a temperature or for too short a time to kill bacteria.

Raw meats carry many bacterial contaminants. The United States Food and Drug Administration (FDA) estimates that 60 percent or more of raw poultry sold at retail carries some disease-causing bacteria. Other raw meat products and eggs are contaminated to a lesser degree. Although thorough cooking kills bacteria and makes the food harmless, recontamination can occur in properly cooked food if it comes into contact with cutting boards, countertops, or utensils that were used with raw meat and not cleaned and sanitized after use. Food can also become contaminated by environmental contaminants and by food handlers carrying bacteria on their hands while preparing foods for the public.

It is estimated that 50 percent of healthy people have staphylococcus organisms in their nasal passages and throats and on their skin and hair. Rubbing a runny nose and then touching food can introduce the bacteria into cooked food. Bacteria flourish at room temperature and grow rapidly in quantities capable of causing illness. To prevent this growth, food must be kept hot or cold but never just warm or at room temperature.

Travel to countries where less attention is paid to sanitation, water purification, and good food-handling practices may expose individuals to bacterial contaminants. Institutional food preparation also increases the risk of food poisoning, especially if food is allowed to stand on warming trays, under warming lights, or at room temperature before being served.

Transmission

Food poisoning is not spread from one individual to another but through direct contact with the causative bacteria, viruses, or other toxins in consumed food.

Demographics

The Centers for Disease Control and Prevention (CDC) estimates that there are from six to 33 million cases of food poisoning in the United States annually, affecting men, women, and children. Food poisoning by E. coli occurs in three out of every 10,000 people. One out of every 1,000 people are reported to have food poisoning caused by Salmonella; two-thirds are young people under age 20, and the majority are children under age nine. Although camplyobacter infections can occur in anyone, children under age five and young adults between ages 15 and 29 are more frequently infected.

Causes and symptoms

Classic food poisoning cases are caused by a variety of bacteria. The most common are the following:

• Salmonella
• Staphylococcus aureus
• Campylobacter jejuni
• Escherichia coli
• Shigella
• Clostridium botulinum

Food poisoning symptoms occur when food-borne bacteria release toxins or poisons as a byproduct of their growth in the body. These toxins (except those from C. botulinum) cause inflammation of the stomach lining and the small and/or large intestines, resulting in abdominal muscle cramps, vomiting, diarrhea, and fever. The severity of symptoms depends on the type of bacteria, the amount consumed, and the individual's general health and sensitivity to the toxin. Dehydration can result from loss of fluids through persistent vomiting and diarrhea; it is one of the most frequent and serious complications of food poisoning. When more fluids are being lost than are replaced, dehydration may occur in the very young and in the elderly, as well as in individuals who take diuretics.

Salmonella

A 2001 CDC report states that culture-confirmed cases of salmonella poisoning affected almost 50,000 people in the United States. However, it is believed that between 2 and 4 million unconfirmed cases actually occur each year. Salmonella is found in egg yolks from infected chickens, raw and undercooked poultry and other meats, dairy products, fish, shrimp, and many other foods. The CDC estimates that one of every 50 consumers is exposed to a contaminated egg yolk each year, although thorough cooking kills the bacteria, making the food harmless. Salmonella is also found in feces of pet reptiles such as turtles, lizards, and snakes. Most cases of salmonella poisoning occur in the warm months between July and October.

Symptoms of food poisoning, such as abdominal pain, diarrhea, vomiting, and fever, begin eight to 72 hours after eating food contaminated with salmonella. Symptoms generally last one to five days. Dehydration can be a complication of severe cases with persistent vomiting and/or diarrhea. People generally recover without antibiotic treatment, although they may feel tired for a week or so after the active symptoms subside.

Staphylococcus aureus

Staph organisms are found on humans and in the environment in dust, air, and sewage. The bacteria are spread primarily by food handlers using poor sanitary practices. Almost any food can be contaminated, but salad dressings, milk products, cream pastries, and any food kept at room temperature, rather than hot or cold, are likely candidates. It is difficult to estimate the number of annual cases of Staphylococcus food poisoning because its symptoms are so similar to those caused by other food-borne bacteria. Many cases are mild. Victims may miss a day of school or work but never see a doctor for confirmation of food poisoning. Symptoms appear rapidly, usually one to six hours after the contaminated food is eaten. Acute symptoms of vomiting and severe abdominal cramps without fever usually last three to six hours and rarely more than 24 hours. Most people recover without medical assistance. Deaths are rare.

Escherichia coli (E. coli)

The many strains of E. coli are not all harmful. Nonpathogenic E. coli are, in fact, a major part of normal gut flora. The strain that causes the most severe food poisoning, however, is E. coli O157:H7, which affects three people in every 10,000. The food-borne organisms are found and transmitted mainly in food derived from cows, such as raw milk and raw or rare ground beef. Fruit or vegetables can also be contaminated.

Symptoms of E. coli poisoning are slower to appear than those caused by other food-borne bacteria. Because E. coli toxins are produced in the large intestine rather than higher up in the digestive system, symptoms typically occur from one to three days after eating contaminated food. Those affected have severe abdominal cramps and watery diarrhea that usually becomes bloody within 24 hours, a condition that can last from one to eight days. There is little or no fever and vomiting occurs only rarely.

Campylobacter jejuni

Campylobacter is the leading cause of bacterial diarrhea worldwide, responsible for more cases (2 million or more) of bacterial diarrhea in the United States than Shigella and Salmonella combined. Campylobacter is carried by healthy cattle, chickens, birds, and flies. It is also found in ponds and stream water and has been found in bottled water and on salad vegetables washed with water. Although eating chicken is a known risk factor, drinking water and eating salads have not been considered significant risks until studies of causes released in 2003 showed possible association with Campylobacter diarrheal infections. It is not known whether contamination occurs at the site of production or in the home or institution after contact with other contaminated foods, surfaces, or utensils. The ingestion of only a few hundred Campylobacter bacteria can cause food poisoning symptoms, which may begin two to five days after eating contaminated food. Symptoms will typically include fever, abdominal pain, nausea, headache, muscle pain, and diarrhea. The diarrhea can be watery or sticky and may contain blood. Symptoms last from seven to ten days and relapses occur in about one-fourth of infected individuals. Dehydration is a common complication. Other complications, such as arthritis-like joint pain and hemolytic-uremic syndrome (HUS), occur in rare cases.

Shigella

Shigella is a common cause of diarrhea in travelers to developing countries. It is associated with contaminated food and water, crowded living conditions, and poor sanitation. The bacterial toxins affect the small intestine. Symptoms of Shigella infection appear about 36–72 hours after eating contaminated food. In addition to the familiar watery diarrhea, nausea, vomiting, and abdominal cramps, the individual may also have chills, fever, and neurological symptoms. The diarrhea may be quite severe with cramping and progresses to classic dysentery. Up to 40 percent of children with severe infections show neurological symptoms. These include confusion, headache, lethargy, a stiff neck, and possible seizures. The symptoms of food poisoning by Shigella organisms may resemble meningitis and a differential diagnosis must be made by isolating the causative bacteria.

The disease runs its course usually in two to three days but may last longer. Dehydration is a common complication. Most people recover on their own, although they may feel exhausted. Children who are malnourished or have weakened immune systems may be severely affected and death can result.

Clostridium botulinum

C. botulinum causes both adult and infant botulism and differs significantly from other contaminants in its sources and symptoms. C. botulinum's common food-borne form is an anaerobic bacterium that can only live and reproduce in the absence of oxygen. Exposure to the botulinum toxin usually occurs while eating contaminated food stored in an airless environment, as in home-canned or commercially canned or vacuum-packed food. Also, botulinum toxin is a neurotoxin that blocks the ability of motor nerves to release acetylcholine, the neurotransmitter that relays nerve signals to muscles. This neurological process can result in unresponsive muscles, a condition known as flaccid paralysis. Breathing may be severely compromised in progressive botulism because of failure of the muscles that control the airway and breathing. In infants, botulism may be caused by specific types of clostridia obtained from soil, inhaled spores, or honey containing the spores. Contamination from any of the sources results in growth of the bacteria in the infant's intestine and production of the neurotoxin.

Infant botulism is a form of botulism first recognized in 1976 that differs from food-borne botulism. Infant botulism occurs when a child younger than one year ingests the spores of C. botulinum. Although these spores are commonly found in soil, honey is a more frequent source of spores causing infant botulism by lodging in the baby's intestinal tract and producing the neurotoxin. Onset of symptoms is gradual. Initially, the baby is constipated, followed by poor feeding, lethargy, weakness, drooling, and a distinctive wailing cry. Eventually, the baby loses the ability to control its head muscles. From there the paralysis progresses to the rest of the body. Immediate treatment is required to avoid neurological complications and death. Infant botulism is much more likely to be fatal than other food poisoning infections. Infant botulism is a special form of food poisoning not related to the food-borne toxins that cause adult botulism.

Adult botulism outbreaks are usually associated with toxins found in home-canned food, although poisoning occasionally results from eating commercially canned or vacuum-packed foods. C. botulinum grows well in non-acidic, oxygen-free environments, meaning that if the cooking temperatures are too low or the cooking time too brief the bacteria in the food are not killed. Instead, bacteria may reproduce inside the can or jar, releasing the deadly neurotoxin. Heating canned food to boiling for ten minutes can render the toxin harmless. However, consuming even a very small amount of the toxin can result in serious illness or death because of lethal neurological complications.

Symptoms of adult botulism appear about 18–36 hours after the contaminated food is eaten, although times of onset have been documented ranging from four hours to eight days. Initially a person suffering from botulism feels weak and dizzy and later experiences double vision. Symptoms progress to difficulty speaking and swallowing. Paralysis moves down the body, and when the respiratory muscles are paralyzed, death can result from asphyxiation. Individuals with any signs of botulism poisoning must receive immediate emergency medical care to increase their chance of survival.

When to call the doctor

Any unexplained abdominal pain accompanied by persistent vomiting or diarrhea, whether or not a food source is suspected, should be reported to the doctor. A child having difficulty swallowing, speaking, holding the head up, or maintaining an upright posture should receive emergency medical attention. Signs of confusion, lethargy, headache, stiff neck, or seizures also require immediate medical attention.

Diagnosis

One important part of diagnosing food poisoning is the need for doctors and community health professionals to determine if a number of people have eaten the same food and show the same symptoms. If this can be proven, food poisoning is strongly suspected. The diagnosis is confirmed when the suspected bacteria is identified in the culture of a stool sample or a fecal smear from the affected individual. In some cases, the suspected bacteria, virus, or toxin can be identified in the actual food source.

Laboratory tests are used to make a definitive diagnosis, but treatment of symptoms may be started immediately without waiting for test results, which may take up to two days. Diagnostic tests focus on identifying the organism causing the illness. This process may involve performing a culture on contaminated material from the suspect food, a stool sample, or swabs of the nose or throat of the affected individual if inhaled spores are a possibility. Culture results are available from the microbiology laboratory as soon as bacteria grow in a special plate incubated at temperatures at or above body temperature. The growth of specific bacteria confirms the diagnosis. The microbiology laboratory may use samples of the bacteria grown to perform other special techniques to help identify the causative organism.

In infant botulism, the infant's stool may be cultured to isolate the organism; this test may be performed by the state health department or the Centers for Disease Control (CDC). Early diagnosis of botulism is critical so that treatment can begin in time to avoid neurological involvement. Although the definitive diagnosis comes from laboratory tests, it can usually be diagnosed by recognizing the distinctive neurological symptoms typical of contamination with C. botulinum.

While waiting for diagnostic test results, the doctor performs a physical examination and may ask about recently consumed food, possible open sores, recent activities and behavior, and other information that may help to rule out other disease possibilities. Imaging studies or additional diagnostic tests may be done to rule out other diseases or conditions with similar symptoms.

Many cases of food poisoning go undiagnosed, since a definite diagnosis is not necessary to effectively treat the symptoms. Because it takes time for symptoms to develop, the most recent food one has eaten may not be the cause of the symptoms.

Treatment

Treatment of food poisoning, except for botulism, focuses on preventing or correcting dehydration by replacing critical fluids and electrolytes lost through vomiting and diarrhea. Electrolytes are mineral salts that form electrically charged particles (ions) in body fluids; they help control body fluid balance and participate in many essential body functions. Pharmacists can recommend effective, pleasant-tasting, electrolyte replacement fluids that are available without a prescription. To prevent dehydration, a doctor may decide to give fluids intravenously. In very serious cases of food poisoning, medications may be given to stop abdominal cramping and vomiting. Antidiarrheal medications are not usually given. Stopping the diarrhea actually maintains toxin levels in the body for longer periods and may prolong the infection. Severe bacterial food poisonings are sometimes treated with intravenous antibiotics.

Modifying the diet while recovering from food poisoning is usually recommended. During a period of active vomiting and diarrhea, solid food should be avoided and only small quantities of clear liquids should be consumed as frequently as possible. Once active symptoms stop, bland, soft, easy-to-digest foods should be consumed for two to three days. One example is the BRAT diet of bananas, rice, applesauce, and toast, all of which are easy to digest. Milk products, spicy food, and fresh fruit should be avoided for a few days, although babies should continue to breastfeed. These modifications are often the only treatment that is necessary.

Botulism is treated in an entirely different way. Older children and adults can be treated with injections of a specific antitoxin for botulism if it can be administered within 72 hours after symptoms are first observed. If given later, it provides little or no benefit. Infants, however, cannot receive this antitoxin and are usually treated instead with injections of human botulism immune globulin (BIG), an antiserum that neutralizes the botulinum toxin. This antiserum is available in the United States through the Infant Botulism Treatment and Prevention Program in Berkeley, California. Both infants and adults may require hospitalization, often in the intensive care unit. Mechanical ventilators may be used for those whose ability to breathe is impaired and intravenous nutrition may be provided until any paralysis is corrected.

Alternative treatment

Alternative practitioners offer the same advice as traditional practitioners concerning diet modification, treatment of diarrhea and vomiting, and prevention of dehydration. Charcoal tablets, Lactobacillus acidophilus, Lactobacillus bulgaricus, and citrus seed extract can be taken to help normalize the digestive system. An electrolyte replacement fluid can be made at home by adding one teaspoon of salt and four teaspoons of sugar to one quart of water. For food poisoning other than botulism, two homeopathic remedies, either Arsenicum album or Nux vomica, are recommended to help reduce symptoms.

Prognosis

Most cases of food poisoning (except botulism) clear up on their own within one week without medical assistance. As symptoms subside, the individual may continue to feel tired or weak for a few days. If dehydration has been effectively corrected or prevented, few complications can be expected. Deaths are rare and usually occur in the very young, the very old, and people whose immune systems are already weakened.

Complications of salmonella food poisoning may include arthritis-like symptoms that occur three to four weeks after infection. Although deaths from salmonella infection are rare, they do occur. Most deaths reported have occurred among elderly adults in long-term care.

Adults usually recover from E. coli poisoning without medical intervention, but many children require hospitalization for contamination with this organism. Toxins may be absorbed into the blood stream where they destroy red blood cells and platelets, tiny cells important in blood clotting. About 5 percent of victims develop hemolytic-uremic syndrome (HUS), which can result in sudden kidney failure that requires a medical procedure (dialysis) to perform the kidney's task of filtering the body's waste products.

Botulism is the deadliest of the bacterial food-borne illnesses. With prompt medical care, the death rate is less than 10 percent in children and adults.

Prevention

Food poisoning is almost entirely preventable by practicing good sanitation and good food handling techniques. These include the following measures:

• Keep hot foods hot and cold foods cold.
• Cook meat to the recommended internal temperature.
• Use a meat thermometer to check meat and cooking eggs until they are no longer runny.
• Refrigerate leftovers promptly, not letting food stand at room temperature.
• Before preparing other foods, carefully clean surfaces (cutting boards and counters, knives and other utensils) contaminated with the juices of uncooked meats.
• Do not refreeze meat once it has been thawed.
• Wash fruits and vegetables before using.
• Consume only pasteurized dairy products and fruit juices.
• Discard bulging or leaking cans or any food that smells spoiled.
• Wash hands well before and during food preparation and after using the bathroom.
• Sanitize food preparation surfaces regularly.

It is especially important to discard any food that seems spoiled and not to eat food that has been stored at room temperature or above for more than a few hours. Home canners must be diligent about using sterile equipment and following U.S. Department of Agriculture canning guidelines.

Infant botulism is perhaps the most difficult poisoning to prevent, because what goes into an infant's mouth is often beyond control. One important preventative measure, however, is to avoid feeding honey to infants younger than 12 months since it is a known source of botulism spores. As infants begin eating solid foods, the same food precautions should be followed as for older children and adults.

Parental concerns

Symptoms of food poisoning can appear as early as an hour after consuming the contaminated food or up to several days later. Parents may be concerned about possible contamination from unknown sources and that symptoms may occur suddenly, without warning. Practicing good sanitation and good food handling techniques is the best way parents can prevent contamination. Normal watchfulness of the parents is sufficient to notice symptoms, paying attention to any change in eating, unusual crying, increases or decreases in bowel movements, the presence of vomiting or a lack of normal responses such as turning of the head and body movements. An early report of symptoms, even if no particular food is suspected of causing illness, helps get early treatment and avoid complications.

See also Botulism; Gastroenteritis.

Resources

BOOKS

Cerexhe, Peter, et al. Risky Food, Safer Choices: Avoiding Food Poisoning. Boulder, Co: netLibrary, 2000.

Isle, Mick. Everything You Need to Know about Food Poisoning. New York: Rosen Publishing Group, 2001.

Rue, Nancy, and Anne Williams. Quick Reference to Food Safety and Sanitation. Boston, MA: Prentice Hall, 2002.

Trickett, Jill. The Prevention of Food Poisoning. Cheltenham, UK: Nelson Thornes, 2001.

ORGANIZATIONS

Centers for Disease Control and Prevention. 1600 Clifton Rd., NE, Atlanta, GA 30333. Web site: <www.cdc.gov>.

WEB SITES

"Food Safety." Available online at <www.nlm.nih.gov/medlineplus/print/foodsafety.html> (accessed November 20, 2004).

L. Lee Culvert Suzanne M. Lutwick, MPH

Foodborne illness (also foodborne disease) is any illness resulting from the consumption of food.

Foodborne illness is commonly called food poisoning, even though most cases are caused by a variety of pathogenic bacteria, viruses, prions or parasites that contaminate food, rather than chemical or natural toxins.

Causes

Foodborne illness usually arises from improper handling, preparation, or food storage. Good hygiene practices before, during, and after food preparation can reduce the chances of contracting an illness. The action of monitoring food to ensure that it will not cause foodborne illness is known as food safety. Foodborne disease can also be caused by a large variety of toxins that affect the environment. For foodborne illness caused by chemicals, see Food contaminants.

Foodborne illness can also be caused by pesticides or medicines in food and naturally toxic substances like poisonous mushrooms or reef fish. Some could even come from the skin and nose, like staphylococcus aureus, which could lead to death.

Symptoms and mortality

Symptoms typically begin several hours to several days after consumption and depending on the agent involved, can include one or more of the following: nausea, abdominal pain, vomiting, diarrhea, gastroenteritis, fever, headache or fatigue.

In most cases the body is able to permanently recover after a short period of acute discomfort and illness. However, foodborne illness can result in permanent health problems or even death, especially for people at high risk, including babies, young children, pregnant women (and their fetuses), elderly people, sick people and others with weak immune systems.

Foodborne illness is a major cause of reactive arthritis, which typically occurs 1–3 weeks afterward. Similarly, people with liver disease are especially susceptible to infections from Vibrio vulnificus, which can be found in oysters or crabs.

Tetrodotoxin poisoning from reef fish and other animals manifests rapidly as numbness and shortness of breath, and is often fatal.

Incubation period

The delay between consumption of a contaminated food and appearance of the first symptoms of illness is called the incubation period. This ranges from hours to days (and rarely months or even years, such as in the case of Listeriosis or Creutzfeldt-Jacob disease), depending on the agent, and on how much was consumed. If symptoms occur within 1–6 hours after eating the food, it suggests that it is caused by a bacterial toxin or a chemical rather than live bacteria.

The long incubation period of many foodborne illnesses tends to cause sufferers to attribute their symptoms to "stomach flu."

During the incubation period, microbes pass through the stomach into the intestine, attach to the cells lining the intestinal walls, and begin to multiply there. Some types of microbes stay in the intestine, some produce a toxin that is absorbed into the bloodstream, and some can directly invade the deeper body tissues. The symptoms produced depend on the type of microbe.

Infectious dose

The infectious dose is the amount of agent that must be consumed to give rise to symptoms of foodborne illness, and varies according to the agent and the consumer's age and overall health. In the case of Salmonella a relatively large inoculum of 1 million to 1 billion organisms is necessary to produce symptoms in healthy human volunteers , as Salmonellae are very sensitive to acid. An unusually high stomach pH level (low acidity) greatly reduces the number of bacteria required to cause symptoms by a factor of between 10 and 100.

Pathogenic agents

Bacteria

Bacteria are a common cause of foodborne illness. In the United Kingdom during 2000 the individual bacteria involved were as follows: Campylobacter jejuni 77.3%, Salmonella 20.9%, H7 1.4%, and all others less than 0.1% . In the past, bacterial infections were thought to be more prevalent because few places had the capability to test for norovirus and no active surveillance was being done for this particular organism. Symptoms for bacterial infections are delayed because the bacteria need time to multiply. They are usually not seen until 12–72 hours or more after eating contaminated food.

Most common bacterial foodborne pathogens are:

• Campylobacter jejuni which can lead to secondary Guillain-Barré syndrome and periodontitis
• Clostridium perfringens, the "cafeteria germ"
• Salmonella spp. - its S. Typhimurium infection is caused by consumption of eggs that are not adequately cooked or by other interactive human-animal pathogens ^{, ,} .
• H7 enterohemorrhagic (EHEC) which causes hemolytic-uremic syndrome

Other common bacterial foodborne pathogens are:

• Bacillus cereus
• Escherichia coli, other virulence properties, such as enteroinvasive (EIEC), enteropathogenic (EPEC), enterotoxigenic (ETEC), enteroaggregative (EAEC or EAgEC)
• Listeria monocytogenes
• Shigella spp.
• Staphylococcus aureus
• Streptococcus
• Vibrio cholerae, including O1 and non-O1
• Vibrio parahaemolyticus
• Vibrio vulnificus
• Yersinia enterocolitica and Yersinia pseudotuberculosis

Less common bacterial agents:

• Brucella spp.
• Corynebacterium ulcerans
• Coxiella burnetii or Q fever
• Plesiomonas shigelloides

Exotoxins

In addition to disease caused by direct bacterial infection, some foodborne illnesses are caused by exotoxins which are excreted by the cell as the bacterium grows. Exotoxins can produce illness even when the microbes that produced them have been killed. Symptoms typically appear after 1–6 hours depending on the amount of toxin ingested.

• Clostridium botulinum
• Clostridium perfringens
• Staphylococcus aureus
• Bacillus cereus

For example Staphylococcus aureus produces a toxin that causes intense vomiting. The rare but potentially deadly disease botulism occurs when the anaerobic bacterium Clostridium botulinum grows in improperly canned low-acid foods and produces botulin, a powerful paralytic toxin. The disease of MMS was recently diagnosed for the first time in the United States in Tucson, Arizona. Symptoms include nausea, fatigue and excessive vomiting. This disease is caused from eating meat sticks that are past an acceptable shelf life.

Pseudoalteromonas tetraodonis, certain species of Pseudomonas and Vibrio, and some other bacteria, produce the lethal tetrodotoxin, which is present in the tissues of some living animal species rather than being a product of decomposition.

Mycotoxins and alimentary mycotoxicoses

The term alimentary mycotoxicoses refers to the effect of poisoning by Mycotoxins through food consumption. Mycotoxins have prominently affected on human and animal health such as an outbreak which occurred in the UK in 1960 that caused the death of 100,000 turkeys which had consumed aflatoxin-contaminated peanut meal and the death of 5000 human lives by Alimentary toxic aleukia (ALA) in the USSR in World War II. The common foodborne Mycotoxins include

• Aflatoxins - originated from Aspergillus parasiticus and Aspergillus flavus. They are frequently found in tree nuts, peanuts, maize, sorghum and other oilseeds, including corn and cottonseeds. The pronounced forms of Aflatoxins are those of B1, B2, G1, and G2, amongst which Aflatoxin B1 predominantly targets the liver, which will result in necrosis, cirrhosis, and carcinoma ^, . In the US, the acceptable level of total aflatoxins in foods is less than 20 μg/kg, except for Aflatoxin M1 in milk, which should be less than 0.5 μg/kg . The official document can be found at FDA's website ^, .
• Altertoxins - are those of Alternariol (AOH), Alternariol methyl ether (AME), Altenuene (ALT), Altertoxin-1 (ATX-1), Tenuazonic acid (TeA) and Radicinin (RAD), originated from Alternaria spp. Some of the toxins can be present in sorghum, ragi, wheat and tomatoes ^{, ,} . Some research has shown that the toxins can be easily cross-contaminated between grain commodities, suggesting that manufacturing and storage of grain commodities is a critical practice .
• Citrinin -
• Citreoviridin -
• Cyclopiazonic acid -
• Cytochalasins
• Ergot alkaloids / Ergopeptine alkaloids - Ergotamine
• Fumonisins - Crop corn can be easily contaminated by the fungi Fusarium moniliforme, and its Fumonisin B1 will cause Leukoencephalomalacia (LEM) in horses, Pulmonary edema syndrome (PES) in pigs, liver cancer in rats and Esophageal cancer in humans ^, . For human and animal health, both the FDA and the EC have regulated the content levels of toxins in food and animal feed ^, .
• Fusaric acid -
• Fusarochromanone -
• Kojic acid -
• Lolitrem alkaloids -
• Moniliformin -
• 3-Nitropropionic acid -
• Nivalenol -
• Ochratoxins - In Australia, The Limit of Reporting (LOR) level for Ochratoxin A (OTA) analyses in 20th Australian Total Diet Survey was 1 µg/kg , whereas the EC restricts the content of OTA to 5 µg/kg in cereal commodities, 3 µg/kg in processed products and 10 µg/kg in dried vine fruits .
• Oosporeine -
• Patulin - Currently, this toxin has been advisably regulated on fruit products. The EC and the FDA have limited it to under 50 µg/kg for fruit juice and fruit nectar, while limits of 25 µg/kg for solid-contained fruit products and 10 µg/kg for baby foods were specified by the EC ^,
• Phomopsins -
• Sporidesmin A -
• Sterigmatocystin -
• Tremorgenic mycotoxins - Five of them have been reported to be associated with molds found in fermented meats. These are Fumitremorgen B, Paxilline, Penitrem A, Verrucosidin, and Verruculogen .
• Trichothecenes - sourced from Cephalosporium, Fusarium, Myrothecium, Stachybotrys and Trichoderma. The toxins are usually found in molded maize, wheat, corn, peanuts and rice, or animal feed of hay and straw ^, . Four trichothecenes, T-2 toxin, HT-2 toxin, diacetoxyscirpenol (DAS) and deoxynivalenol (DON) have been most commonly encountered by humans and animals. The consequences of oral intake of, or dermal exposure to, the toxins will result in Alimentary toxic aleukia, neutropenia, aplastic anemia, thrombocytopenia and/or skin irritaion ^{, ,} . In 1993, the FDA issued a document for the content limits of DON in food and animal feed at an advisory level . In 2003, US published a patent that is very promising for farmers to produce a trichothecene-resistant crop .
• Zearalenone -
• Zearalenols -

Emerging foodborne pathogens

Much is still not known about foodborne illness. Approximately sixty percent of outbreaks are still caused by unknown sources.

• Aeromonas hydrophila, Aeromonas caviae, Aeromonas sobria

Preventing bacterial food poisoning

Prevention is mainly the role of the state, through the definition of strict rules of hygiene and a public services of veterinary surveying of animal products in the food chain, from farming to the transformation industry and delivery (shops and restaurants). This regulation includes:

• traceability: in a final product, it must be possible to know the origin of the ingredients (originating farm, identification of the harvesting or of the animal) and where and when it was processed; the origin of the illness can thus be tracked and solved (and possibly penalized), and the final products can be removed from the sale if a problem is detected;
• enforcement of hygiene procedures like HACCP and the "cold chain";
• power of control and of law enforcement of veterinarians.

In August 2006, the United States Food and Drug Administration approved Phage therapy which involves spraying meat with viruses that infect bacteria, and thus preventing infection. This has raised concerns, because without mandatory labelling consumers wouldn't be aware that meat and poultry products have been treated with the spray.

At home, prevention mainly consists of good food safety practices. Many forms of bacterial poisoning can be prevented even if food is contaminated by cooking it sufficiently, and either eating it quickly or refrigerating it effectively. Many toxins, however, are not destroyed by heat treatment.

Viruses

Viral infections make up perhaps one third of cases of food poisoning in developed countries. In the US, more than 50% of cases are viral and noroviruses are the most common foodborne illness, causing 57% of outbreaks in 2004. Foodborne viral infection are usually of intermediate (1–3 days) incubation period, causing illnesses which are self-limited in otherwise healthy individuals, and are similar to the bacterial forms described above.

• Enterovirus
• Hepatitis A is distinguished from other viral causes by its prolonged (2–6 week) incubation period and its ability to spread beyond the stomach and intestines, into the liver. It often induces jaundice, or yellowing of the skin, and rarely leads to chronic liver dysfunction. The virus has been found to cause the infection due to the consumption of fresh-cut produce which has fecal contamination ^, .
• Hepatitis E
• Norovirus
• Rotavirus

Parasites

Most foodborne parasites are zoonoses.

Platyhelminthes:

• Diphyllobothrium sp.
• Nanophyetus sp.
• Taenia saginata
• Taenia solium
• Fasciola hepatica

See also: Tapeworm and Flatworm

Nematode:

• Anisakis sp.
• Ascaris lumbricoides
• Eustrongylides sp.
• Trichinella spiralis
• Trichuris trichiura

Protozoa:

• Acanthamoeba and other free-living amoebae
• Cryptosporidium parvum
• Cyclospora cayetanensis
• Entamoeba histolytica
• Giardia lamblia
• Sarcocystis hominis
• Sarcocystis suihominis
• Toxoplasma gondii

Natural toxins

Several foods can naturally contain toxins, many of which are not produced by bacteria. Plants in particular may be toxic; animals which are naturally poisonous to eat are rare. In evolutionary terms, animals can escape being eaten by fleeing; plants can use only passive defenses such as poisons and distasteful substances, for example capsaicin in chili peppers and pungent sulfur compounds in garlic and onions. Most animal poisons are not synthesised by the animal, but acquired by eating poisonous plants to which the animal is immune, or by bacterial action.

• Alkaloids
• Ciguatera poisoning
• Grayanotoxin (honey intoxication)
• Mushroom toxins
• Phytohaemagglutinin (red kidney bean poisoning; destroyed by boiling)
• Pyrrolizidine alkaloid
• Shellfish toxin, including paralytic shellfish poisoning, diarrhetic shellfish poisoning, neurotoxic shellfish poisoning, amnesic shellfish poisoning and ciguatera fish poisoning
• Scombrotoxin
• Tetrodotoxin (fugu fish poisoning)

Some plants contain substances which are toxic in large doses, but have therapeutic properties in appropriate dosages.

• Foxglove contains cardiac glycosides.
• Poisonous hemlock (conium) has medicinal uses.

Other pathogenic agents

• Prions, resulting in Creutzfeldt-Jakob disease

"Ptomaine poisoning"

An early theory on the causes of food poisoning involved ptomaines (from Greek ptōma, "fall, fallen body, corpse"), alkaloids found in decaying animal and vegetable matter. While some alkaloids do cause poisoning, the discovery of bacteria left the ptomaine theory obsolete and the word "ptomaine" is no longer used scientifically.

Global Impact

In modern times, rapid globalization of food production and trade has increased the potential likelihood of food contamination. Many outbreaks of foodborne diseases that were once contained within a small community may now take place on global dimensions. Food safety authorities all over the world have acknowledged that ensuring food safety must not only be tackled at the national level but also through closer linkages among food safety authorities at the international level. This is important for exchanging routine information on food safety issues and to have rapid access to information in case of food safety emergencies."

It is difficult to estimate the global incidence of foodborne disease, but it has been reported that in the year 2000 about 2.1 million people died from diarrhoeal diseases. Many of these cases have been attributed to contamination of food and drinking water. Additionally, diarrhoea is a major cause of malnutrition in infants and young children.

Even in industrialized countries, up to 30% of the population of people have been reported to suffer from foodborne diseases every year. In the U.S, around 76 million cases of foodborne diseases, which resulted in 325,000 hospitalizations and 5,000 deaths, are estimated to occur each year. Developing countries in particular, are worst affected by foodborne illnesses due to the presence of a wide range of diseases, including those caused by parasites. Foodborne illnesses can and did inflict serious and extensive harm on society. In 1994, an outbreak of salmonellosis due to contaminated ice cream occurred in the USA, affecting an estimated 224,000 persons. In 1988, an outbreak of hepatitis A, resulting from the consumption of contaminated clams, affected some 300,000 individuals in China.

Food contamination creates an enormous social and economic strain on societies. In the U.S., diseases caused by the major pathogens alone are estimated to cost up to US $35 billion annually (1997) in medical costs and lost productivity. The re-emergence of cholera in Peru in 1991 resulted in the loss of US $500 million in fish and fishery product exports that year.

Statistics

Every year there are about 76 million foodborne illnesses in the United States (26,000 cases for 100,000 inhabitants), 2 million in the United Kingdom (3,400 cases for 100,000 inhabitants) and 750,000 in France (1,210 cases for 100,000 inhabitants).

United States

In the United States, there are approximately 76 million foodborne illnesses (26,000 cases for 100,000 inhabitants):

• 325,000 were hospitalized (111 per 100,000 inhabitants);
• 5,000 people died (1.7 per 100,000 inhabitants.).
• Major pathogens from food borne illness in the United States cost upwards of US $35 billion dollars in medical costs and lost productivity (1997)

France

In France, for 750,000 cases(1,210 per 100,000 inhabitants):

• 70,000 people consulted in the emergency department of an hospital (113 per 100,000 inhab.);
• 113,000 people were hospitalized (24 per 100,000 inhabitants);
• 400 people died (0.9 per 100,000 inhabitants).

Australia

In Australia, there are an estimated 5.4 million cases of food-borne illness every year, causing:

• 18,000 hospitalisations
• 120 deaths
• 2.1 million lost days off work
• 1.2 million doctor consultations
• 300,000 prescriptions for antibiotics

Causes of foodborne illness in France

	Cause	Annual cases	Rate (per 100,000 inhabitants)
1	Salmonella	~8,000 cases	13
2	Campylobacter	~3,000 cases	4.8
3	Parasites incl. Toxoplasma	~500 cases ~400 cases	0.8 0.65
4	Listeria	~300 cases	0.5
5	Hepatitis A	~60 cases	0.1

Causes of death by foodborne illness in France

	Cause	Annual	Rate (per 100,000 inhabitants)
1	Salmonella	~300 cases	0.5
2	Listeria	~80 cases	0.13
3	Parasites	~37 cases	0.06 (95% due to toxoplasma)
4	Campylobacter	~15 cases	0.02
5	Hepatitis A	~2 cases	0.003

Outbreaks

The vast majority of reported cases of foodborne illness occur as individual or sporadic cases. The origin of most sporadic cases is undetermined. In the United States, where people eat outside the home frequently, most outbreaks (58%) originate from commercial food facilities (2004 FoodNet data). An outbreak is defined as occurring when two or more people experience similar illness after consuming food from a common source.

Often, a combination of events contributes to an outbreak, for example, food might be left at room temperature for many hours, allowing bacteria to multiply which is compounded by inadequate cooking which results in a failure to kill the dangerously elevated bacterial levels.

Outbreaks are usually identified when those affected know each other. However, more and more, outbreaks are identified by public health staff from unexpected increases in laboratory results for certain strains of bacteria. Outbreak detection and investigation in the United States is primarily handled by local health jurisdictions and is inconsistent from district to district. It is estimated that 1–2% of outbreaks are detected.

Political issues

United Kingdom

In the UK serious outbreaks of foodborne illness since the 1970s prompted key changes in UK food safety law. These included the death of 19 patients in the Stanley Royd Hospital outbreak and the bovine spongiform encephalopathy (BSE, mad cow disease) outbreak identified in the 1980s. The death of 17 people in the 1996 Wishaw outbreak of E. coli O157 was a precursor to the establishment of the Food Standards Agency which, according to Tony Blair in the 1998 white paper A Force for Change Cm 3830 "would be powerful, open and dedicated to the interests of consumers".

United States

In 2001, the Center for Science in the Public Interest (CSPI) petitioned the United States Department of Agriculture to require meat packers to remove spinal cords before processing cattle carcasses for human consumption, a measure designed to lessen the risk of infection by variant Creutzfeldt-Jakob disease. The petition was supported by the American Public Health Association, the Consumer Federation of America, the Government Accountability Project, the National Consumers League, and Safe Tables Our Priority. This was opposed by the National Cattlemen's Beef Association, the National Renderers Association, the National Meat Association, the Pork Producers Council, sheep raisers, milk producers, the Turkey Federation, and eight other organizations from the animal-derived food industry. This was part of a larger controversy regarding the United States' violation of World Health Organization proscriptions to lessen the risk of infection by variant Creutzfeldt-Jakob disease.

None of the US Department of Health and Human Services targets regarding incidence of foodborne infections were reached in 2007

Organizations

World Health Organization Food Safety Department The WHO provides scientific advice for organizations and the public on issues concerning the safety of food. It serves as a medium linking the food safety systems in countries around the world. Food safety is currently one of WHO's top ten priorities. Food Safety is one of the major issues in our world today, and the Organization calls for more systematic and aggressive steps to be taken to significantly reduce the risk of foodborne diseases.

The Department of Food Safety, Zoonoses and Foodborne Diseases The Department of Food Safety, Zoonoses and Foodborne Diseases is a department under the WHO. Its mission is to: to reduce the serious negative impact of foodborne diseases worldwide. According to the WHO website, food and waterborne diarrhoeal diseases are leading causes of illness and death in less developed countries, killing approximately 1.8 million people annually, most of whom are children "WHO works closely with the Food and Agriculture Organization of the United Nations (FAO) to address food safety issues along the entire food production chain--from production to consumption--using new methods of risk analysis. These methods provide efficient, science-based tools to improve food safety, thereby benefiting both public health and economic development."

The International Food Safety Authorities Network (INFOSAN) This Network is intended to complement and support the existing WHO Global Outbreak Alert and Response Network (GOARN) which includes a Chemical Alert and Response component.

Academic resources

Periodicals

• International Journal of Food Microbiology, ISSN: 0168-1605, Elsevier
• Foodborne Pathogens and Disease, ISSN: 1535-3141, Mary Ann Liebert, Inc.
• Mycopathologia, ISSN: 1573-0832 (electronic) 0301-486X (paper), Springer

Books

• Advances in Food Mycology (Advances in Experimental Medicine and Biology) (2006) by A.D. Hocking et al., ISBN-13: 978-0387283913 (electronic) 978-0387283852 (paper), Springer
• Foodborne Infections and Intoxications (2006) by Hans P. Riemann and Dean O. Cliver, ISBN 012588365X, Elsevier
• Foodborne Pathogens: Microbiology And Molecular Biology (2005) by Pina M. Fratamico et al., ISBN-10: 190445500X ISBN-13: 978-1904455004, Caister Academic Press

See also

• List of foodborne illness outbreaks by country
• 1984 Rajneeshee bioterror attack
• 2006 North American E. coli outbreak
• Alexander Litvinenko poisoning
• Attack rate
• United States Disease Control and Prevention
• Food allergy

• Food hygiene
• Food quality
• Food Microbiology
• Food safety
• Food Testing Strips
• Gastroenteritis

• Juice
• List of infectious diseases
• List of poisonings
• Mycotoxicology
• Minamata disease
• Munir Said Thalib
• Risk assessment
• Zoonotic pathogens

References

External links

• Surveillance for Foodborne-Disease Outbreaks --- United States, 1998--2002
• Food Poisoning FAQ from About.com
• Preventing Food Poisoning
• VeriPrime Food Safety Alliance New Farm to Fork Food Safety System
• Food Safety News FoodSQM.com
• Foodborne diseases, emerging, WHO, Fact sheet N°124, revised January 2002
• Foodborne illness information pages, NSW Food Authority
• Food safety and foodborne illness, WHO, Fact sheet N°237, revised January 2002
• UK Health protection Agency
• US PulseNet
• Nottingham Trent University Foodborne illness research data
• Safe Tables Our Priority (S.T.O.P.)
• Food and Drink Federation Guide
• Salmonella food poisoning
• Bacterial Food Poisoning
• BBC Information
• Medline
• UK NHS Information
• Food Safety Network
• Open Directory Food and Water Borne Diseases Category
• Food poisoning basics
• The World Health Organization
• The United States FDA
• Food Standard Agency website
• The Canadian Food Inspection Agency Website
• Symptoms and effects of 8 common foodborne illnesses
• Genome information for some of the organisms causing foodborne illness (diarrheagenic E. coli and Salmonella) is available from the NIAID Enteropathogen Resource Integration Center (ERIC)
• J. Fosse, H. Seegers, C. Magras (2008). Foodborne zoonoses due to meat: a quantitative approach for a comparative risk assessment applied to pig slaughtering in Europe. Veterinary Research, 39:01