Foodborne Illness


Foodborne illness is a disease or infection caused by consuming food contaminated with disease-causing organisms such as bacteria, viruses, and parasites, or naturally occurring toxins present in the food itself (such as the poisons in some mushrooms). Harmful environmental toxins such as pesticides, fertilizers, and disinfectants can also contaminate foods and sometimes cause foodborne illness. The symptoms of foodborne illnesses are usually stomach upset, diarrhea, nausea, and vomiting. Clinically, foodborne illness can be called gastroenteritis or infectious diarrhea. It may also be called food poisoning.


Foodborne illness is a serious public health concern in the United States and around the world. More than 250 foodborne illnesses have been identified. Most are infections caused by pathogenic microorganisms. Ingested pathogens adhere to the lining of the intestines, where they begin to multiply. Some pathogens remain in the intestines and produce toxins that enter the bloodstream. Others invade deeper body tissues. Symptoms can be caused by toxins secreted by the microbes or by the body's immune reaction to the presence of the causal microbe.

WHO Foodborne Diseases Estimates, 2015

WHO Foodborne Diseases Estimates, 2015
SOURCE: World Health Organization (WHO).

Thorough cooking kills most pathogenic microorganisms. However, major outbreaks of foodborne illness from contaminated beef, peanut butter, fresh produce such as lettuce, and other foods have raised public awareness of foodborne illness. The U.S. Centers for Disease Control and Prevention (CDC) estimates that about 97% of foodborne illnesses result from improper food handling, such as undercooking, improper refrigeration, or cross-contamination of foods. About 80% of these cases occur in restaurants, cafeterias, or institutions such as nursing homes and prisons. The remaining 20% are due to improper food handling at home or the use of contaminated food products.

Agents responsible for foodborne illness evolve over time and require constant surveillance. Although improved food safety, including milk pasteurization, safer canning methods, and water treatment, have conquered some foodborne diseases in the developed world, other pathogens have emerged or appear to be on the increase, for example, escherichia coli 0157:H7 and salmonella serotype enteritides.

Although unpleasant, most foodborne illnesses do not require medical treatment, and victims recover within a few hours to a few days. However, the very young, the very old, pregnant women, and individuals with compromised immune systems are more likely to develop severe illness that results in hospitalization and life-threatening complications.

Risk factors

Anyone of any age, gender, or race/ethnicity can acquire a foodborne illness from eating contaminated food. However, certain populations are affected more than others, including young children, older adults, pregnant women, and anyone with a compromised immune system (e.g., individuals with HIV/AIDS, diabetes, liver or kidney disease, and those who are receiving chemotherapy, or those who are receiving immunosuppressant drugs after organ transplant or for autoimmune disease).

Risk of foodborne diseases is highest in low- and middle-income countries (and communities) with unsafe water, poor sanitation practices, poor hygiene, and inadequate food production and storage methods. Lack of food safety legislation and public education increases risk for populations.

The CDC lists five food preparation risk factors that pertain to restaurants or homes and are most often responsible for causing foodborne illnesses: not keeping foods that require temperature control (temperature controlled for safety or TCS foods) at the proper temperature or letting them stand too long; not cooking foods to the right temperature to kill bacteria; using contaminated utensils or equipment; not following personal hygiene rules; and purchasing food from unsafe sources.


Even though the U.S. food supply is among the safest in the world and serious outbreaks of foodborne illness are relatively rare, the CDC reports that 48 million people acquire foodborne illness annually in the United States, of whom 128,000 are hospitalized and 3,000 die. The numbers of individuals are comparable to the number of illnesses and deaths from flu in a typical year. In the United States, foodborne illnesses rise in the summer, as hot, humid weather encourages bacterial growth, and people cook and eat outside without refrigeration, thermostat-controlled cooking, or washing facilities.

Causes and symptoms

Foodborne illnesses are caused by ingesting foods contaminated by many different types of organisms, including bacteria, viruses, and parasites. They are also caused by food-based exposure to environmental toxins (pesticides, fertilizers, herbicides) and chemical exposures (aflatoxin, cassava cyanide, dioxin). The route to contamination varies. Some contaminates in fresh foods are from soil or water contaminated with the feces from animals, other contaminates are added during food preparation, often by non-hygienic practices or infected food handlers. Certain organisms grow in improperly canned or preserved foods. Environmental toxins and chemicals may also contaminate vegetables and fruits where they grow or can be found in the feed of animals used for human consumption. Contaminated meats include meat products from infected animals.

Contamination can occur at any point in the food-production chain:

Causative agents

Pathogens responsible for foodborne illnesses are often not identified. However, the vast majority of those of known origin are caused by one of eight pathogens.

Both listeriosis and salmonellosis can be transmitted to a fetus, causing miscarriage, fetal or newborn death, premature delivery, or severe illness in mother and infant. Since most listeriosis outbreaks are caused by contaminated animal products, pregnant women are often advised to avoid deli meats.

Less common but potentially deadly food pathogens include:

Other causes of foodborne illness include toxins in poisonous mushrooms and reef fish, food contaminated with pesticides or herbicides, and certain communicable pathogens that are occasionally foodborne. The latter include hepatitis A virus, rotavirus, and the parasites Giardia and Cryptosporidium.


Almost any food can become contaminated. Foodborne illness is most often associated with poultry, followed, in order of incidence, by leafy greens, beef, diary, fruits and nuts, lettuce, tomatoes and cucumbers, pork, fish, eggs, filter-feeding shellfish, and beans and grains. Raw or undercooked meat, poultry, eggs, fish, and raw (unpasteurized) milk are common sources. Washing fruits and vegetables will reduce but not eliminate pathogens.

Processed foods that pool ingredients from multiple sources are particularly dangerous, since a pathogen from one plant or animal can contaminate an entire batch. A single hamburger can include meat from hundreds of animals. A glass of milk may be pooled from the milk of hundreds of cows. Fruit juice can be made from many individual fruits. A restaurant omelet can contain eggs from hundreds of chickens.

High levels of salt, sugar, or acid prevent bacteria from growing in preserved foods. However, small numbers of bacteria can multiply quickly under warm, moist conditions. A few bacteria in alfalfa or bean seeds can multiply to contaminate an entire batch of sprouts. Although refrigeration or freezing generally prevents bacteria from multiplying, L. monocytogenes and the foodborne bacterium Yersinia enterocolitica can grow and multiply at refrigerator temperatures.


Most foodborne illnesses are characterized by diarrhea, nausea and vomiting, abdominal cramps, and fever. Symptoms generally begin suddenly within one to 48 hours of eating a contaminated food but can be delayed for days. Other symptoms include bloody diarrhea, headache, dizziness, and blurred vision. Diarrhea and vomiting can rapidly cause dehydration (excessive loss of body fluids) especially in children. Worldwide, dehydration is the biggest killer of children under age five.

Illness from foodborne toxins is a medical emergency. In addition to nausea and vomiting, natural toxins in some wild mushrooms can cause hallucinations, coma, and death. Shellfish toxins and Japanese puffer fish poison affect the nervous system, beginning with tingling in the mouth, arms, and legs, followed by dizziness and possibly difficulty breathing. Poisoning with manmade chemicals varies with the type of chemical and degree of exposure.


Treatment for a natural or manmade toxin may require precise identification of the chemical. Extensive blood tests may be required or the patient's stomach may be pumped and its contents tested.


Immediate treatment for foodborne illness is the prevention or reversal of dehydration by replacing fluids and electrolytes lost through vomiting and diarrhea. Small sips of over-the-counter (OTC) oral rehydration solutions should be given to young children as soon as vomiting or diarrhea begin. Antibiotics are not usually required for foodborne illnesses, and antidiarrheal medications may slow the elimination of toxins and pathogens and delay recovery.

Botulism, severe dehydration, or other complications of foodborne illness require hospitalization. Adults are given botulism antitoxin if it can be administered within 72 hours of the appearance of symptoms.


Foodborne illnesses are usually mild and resolve on their own within one to a few days, as the body's immune system kicks in. Botulism is the deadliest bacterial foodborne illness, but when victims receive prompt medical care, the death rate is less than 10%. Other foodborne illnesses can have chronic complications. Campylobacter can cause Guillain-Barré syndrome. E. coli O157:H7 and related bacteria can cause HUS, the most common cause of acute kidney failure in children and fatal in 3%–5% of cases.

Foodborne chemical illness is more likely to cause serious long-term complications. Toxins in some wild mushrooms and fish can cause permanent liver damage. Pesticides and other chemical contaminants can cause liver damage, kidney failure, and nervous system complications.


Foodborne illness is largely preventable through responsible farming, processing, and food-handling practices.

Life-threatening paralytic food poisoning caused by botulinum toxin from the bacterium Clostridium botulinum.
Bacteria found in almost all raw poultry that can cause foodborne illness.
An abnormally low fluid content in the body usually caused by loss of body fluids from vomiting and/or diarrhea.
Ions such as sodium, potassium, calcium, magnesium, chloride, phosphate, bicarbonate, and sulfate that are necessary in the body to regulate most metabolic processes. Loss of fluid balance in the body causes an imbalance in electrolytes that can be dangerous.
Inflammation of the lining of the stomach and intestines.
Hemolytic uremic syndrome (HUS)—
A group of serious conditions (syndrome) caused by Shiga toxin-producing E. coli O157:H7, which can progress to hemolytic anemia (destruction of red blood cells known as hemolysis), kidney failure (uremia), and death. Kidney failure in infants and young children is a serious complication of foodborne illness.
A usually mild foodborne illness caused by Listeria monocytogenes, which can be serious or fatal for fetuses, newborns, the elderly, and immunocompromised patients.
Norwalk virus; a large family of RNA viruses that are a common cause of foodborne illness.
A causative agent of disease, such as a bacterium, virus, or parasite.
Food poisoning by bacteria of the genus Salmonella, which may cause severe diarrhea. Salmonellosis can be transmitted to a fetus.
Shiga toxin-producing E. Coli (STEC)—
A common strain of the normally harmless Escherichia coli intestinal bacterium; it is responsible for most cases of traveler's diarrhea.
Toxoplasma gondii
A common parasite that can cause toxoplasmosis and is a leading cause of death from foodborne illness; although it infects large numbers of people, T. gondii is usually dangerous only in immunocompromised patients and in newly infected pregnant women.

Heating food to an internal temperature of 160°F (78°C) for even a few seconds kills most bacteria, viruses, and parasites. Food thermometers should be used to check the internal temperature of cooking meat, and egg yolks should be cooked until firm. Clostridium spores must be destroyed with temperatures above boiling. Bacterial toxins vary in their heat sensitivity. Botulism toxin is completely inactivated by boiling, but staphylococcal toxin is not. Milk, juice, and cider should be pasteurized. Irradiation of meat and other foods also destroys pathogens.

Public health role and response

Food safety is a critical public health issue as foodborne disease represents a widespread health concern in developed and developing countries. At the local level, healthcare professionals and individuals are urged to report foodborne illnesses to their local health departments so that outbreaks can be detected, traced, and halted. At the national and global levels, organizations such as the CDC and the WHO have active surveillance networks that track outbreaks, identify causal organisms or environmental sources of infection, and work with policy makers to help regulate the food supply and the food industry. The tracking of outbreaks is especially important to the overall effort to reduce the incidence and prevalence of foodborne illness. Publicity surrounding outbreaks of foodborne illness led to passage of the U.S. Food Safety Modernization Act in 2010, with the aim of tightening food-production safety regulations. The growing of food, handling of animals for food consumption, and the processing and packaging of food are targets for curbing food contamination before it starts. Surveillance helps to identify the source of contamination and identify opportunities for preventing contamination and both individual illness and widespread outbreaks of foodborne illness.

Research and general acceptance

Advances in rapid and precise monitoring methods to detect foodborne pathogens are helping to effectively control and prevent human foodborne infections. Although conventional microbiological detection and identification methods are still used to identify foodborne pathogens causing outbreaks, the pathogens are not always able to be identified. Newer nucleic acid methods, micro-nano-bio acoustic systems, and biosensor-based methods are helping to meet the demands of rapid food testing to keep foodborne pathogens from ever reaching kitchens where foods are prepared. Research continues to develop appropriate and accurate means to quickly identify a causal agent and provide more rapid treatment. Research is also ongoing to develop more effective treatment methods at a time when antimicrobial resistance is increasing and threatening human health. Researchers are especially focused on finding effective strategies to fight antimicrobial resistance mechanisms, including developing novel products with antibacterial activity that may be useful not only in treating foodborne illness but also improving food processing and packing methods.

See also Escherichia coli ; Food poisoning ; Food safety ; Listeriosis ; Norovirus ; Parasites ; Viruses .



Duyff, Roberta Larson. Academy of Nutrition and Dietetics Complete Food and Nutrition Guide, 5th ed. New York: Academy of Nutrition and Dietetics, 2017.


Byrne, L., C. Jenkins, N. Launders, et al. “The Epidemiology, Microbiology and Clinical Impact of Shiga Toxin-producing Escherichia Coli in England, 2009–2012.” Epidemiology and Infection. 143 (December 2015): 3475–87.

Ma, D. S. L., L. R. Tan, K. G. Chan, et al. “Resveratrol-Potential Antibacterial Agent against Foodborne Pathogens.” Frontiers in Pharmacology 9 (February 2018): 102–107.

Zhao, X., C. W. Lin, J. Wang, D. H. Oh. “Advances in Rapid Detection Methods for Foodborne Pathogens.” Journal of Microbiology and Biotechnology 24 (March 2014): 297–312.


Centers for Disease Control and Prevention, Foodborne Disease Outbreak Surveillance System (FDOSS) “Frequently Asked Questions and Answers.” Food Safety at CDC. (accessed April 18, 2018).

MedlinePlus. “Foodborne Illness.” (accessed April 18, 2018).

U.S. Food and Drug Administration. “Bad Bug Book: Foodborne Pathogenic Microorganisms and Natural Toxins Handbook.” (accessed April 18, 2018).


Centers for Disease Control and Prevention, 1600 Clifton Rd., Atlanta, GA, 30333, (800) 232-4636),, .

Department of Agriculture, 1400 Independence Ave. SW, Washington, DC, 20250, (202) 720-2791, .

Environmental Protection Agency, 1200 Pennsylvania Ave., NW, Ariel Rios Bldg., Washington, DC, 20460, (202) 272-0167, .

National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, 1600 Clifton Rd., Atlanta, GA, 30333, (800) 232-4635,, .

Partnership for Food Safety Education, 2345 Crystal Dr., Ste. 800, Arlington, VA, 22202, (202) 220-0651, Fax: (202) 220-0873,, .

STOP Foodborne Illness, 3759 N. Ravenswood, Ste. 224, Chicago, IL, 60613, (773) 269-6555, Fax: (773) 883-3098, (800) 350-STOP, .

Margaret Alic, PhD

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