Definition Food-borne illnesses and diseases, or enteric diseases, are transmitted to humans from
infectious organisms in food and water, generally resulting in gastrointestinal
symptoms that vary in severity and duration. Enteric diseases may be caused by
viruses, bacteria, or parasites. Technically, the phrase “food
poisoning” refers to ingestion of food-borne toxins rather
than infectious agents such as bacteria and viruses.
Enteric diseases are thought to cause about 70 percent of cases of diarrhea. Often, what is referred to as a stomach bug or a twenty-four-hour flu is actually the result of a food-borne illness. It is usually difficult to pinpoint the cause of stomach upset because of the long incubation periods for most infectious agents and because exposure occurs several times each day. As a result, epidemiologists believe that for every known case of food-borne illness, dozens more go unreported.
To be confirmed as a case of enteric disease, the illness must lead a person to seek medical care. A stool specimen must be collected and sent to a laboratory, which tests the sample for multiple organisms. If the lab confirms a specific pathogen, it must report the case to the local health department or to the Centers for Disease Control and Prevention (CDC), or both. An outbreak is said to occur when two or more cases can be traced to the same source, as when multiple people become ill after eating the same food at a picnic.
Characteristics Symptoms associated with enteric diseases vary according to the pathogen
responsible, but often include diarrhea, nausea, abdominal pain, vomiting, and
fever. Generally, food-borne illness results in a temporary, uncomfortable period
of stomach upset. A health care provider should be consulted, however, if the
patient has trouble keeping liquids down or has diarrhea that persists for more
than three days and is accompanied by a fever of more than 101.5° Fahrenheit, is
bloody, and leads to dehydration. In addition, an estimated
15 percent of people who experience acute gastroenteritis develop reactive arthritis within four weeks
of infection with Campylobacter,
Salmonella, Shigella, Yersinia,
or, occasionally,
Escherichia coli O157:H7. Symptoms of this type of arthritis
include lower extremity stiffness and pain.
The most common cause of food-borne illness in the United States is the family
of noroviruses (Norwalk virus being the best known). The
incubation period is twelve to forty-eight hours and the illness lasts for twelve
to sixty hours. Symptoms include nausea, vomiting, abdominal cramping, diarrhea,
fever, muscle pain, and headache. Common sources include shellfish and other foods
(such as those in salad bars) contaminated by infected persons.
Campylobacter
infections result in the onset of symptoms two to five days after the consumption of contaminated raw or undercooked poultry, unpasteurized milk, or contaminated water. Symptoms, including diarrhea (sometimes bloody), cramps, fever, and vomiting, last two to ten days.
Salmonella spp. are commonly found in eggs, poultry,
unpasteurized milk and juice, cheese, raw fruits and vegetables (such as sprouts
and melons), and street-vended foods. Most strains of Salmonella
cause symptoms that include diarrhea, fever, cramps, and vomiting. Certain strains
result in typhoid
fever, with fever, headache, constipation, malaise, chills,
and myalgia. Symptoms appear after an incubation period of one to three days and
typically last four to seven days.
Clostridium perfringens infections have an incubation period of eight to sixteen hours after ingestion of a contaminated food, such as meat, poultry, or gravy; and after ingestion of dried or precooked foods or foods left out of a refrigerator or freezer (at room temperature or higher) for too long. Symptoms include watery diarrhea, nausea, and cramping, which last twenty-four to forty-eight hours.
Giardia
is a parasite that causes symptoms one to two weeks after consumption of contaminated water, uncooked food, or food handled by an ill person after cooking. Diarrhea, stomach cramps, and gas can last days or weeks.
Staphylococcus aureus infections commonly result in the sudden onset of severe nausea and vomiting and cramps (and sometimes diarrhea and fever), one to six hours after eating contaminated foods, such as unrefrigerated or improperly stored meats, mayonnaise-based salads, pastries containing cream or cheese, and other prepared foods. Symptoms last twenty-four to forty-eight hours.
E. coli has several forms, most of which are harmless and all of
which are common in the digestive tracts of warm-blooded animals (including
humans). Enterotoxigenic E. coli (ETEC) is a common cause of
travelers’
diarrhea (also known colloquially as Montezuma’s revenge,
Delhi belly, and yalla yalla). ETEC infection typically has a one-to-three-day
incubation period, after which the infected person experiences watery diarrhea,
cramps, and vomiting for three days to one week or more. ETEC is associated with
fecal-contaminated water or food.
Less common, but more serious, forms of E. coli are known as enterohemorrhagic E. coli (EHEC), which include E. coli O157:H7 and other Shiga toxin-producing E. coli (STEC). These forms of E. coli result in severe and often bloody diarrhea, abdominal pain, and vomiting and are more common in children under age four years. Illness manifests one to eight days after consumption of undercooked beef, especially hamburger, unpasteurized milk and juice, raw fruits and vegetables, and contaminated water. EHEC-associated symptoms generally last five to ten days. About 2 to 7 percent of persons infected with E. coli O157:H7 (mostly children and the elderly) develop hemolytic-uremic syndrome, and of those, about one-third develop chronic kidney disease and 3 to 5 percent die. E. coli transmitted from infected poultry and pork products is thought to be a significant cause of the approximately eight million urinary tract infections (UTIs) that the National Institute of Diabetes and Digestive and Kidney Diseases estimates occur each year in the United States as of 2012.
Toxoplasma gondii
is a parasite that infects humans through the ingestion of unwashed fruits and vegetables contaminated by animal feces or the ingestion of raw and partially cooked meat (especially pork, lamb, and venison). The incubation period is five to twenty-three days and symptoms, which are present only in about 20 percent of infected persons, include flulike illness or swollen lymph nodes (or both), which can last months.
Shigella
infections result in symptoms of abdominal cramps, fever, and diarrhea about twenty-four to forty-eight hours after contact with contaminated food and last four to seven days. Shigella is associated with fecal-oral transmission, often spread from an infected food worker to ready-to-eat foods such as raw vegetables, salads, and sandwiches.
Yersinia
infections cause symptoms including diarrhea, vomiting, fever, abdominal pain, and, sometimes, a red rash. Yersinia is associated with undercooked pork, unpasteurized milk, tofu (soy), and contaminated water. Symptoms appear twenty-four to forty-eight hours after infection and last one to three weeks. Rarely, Yersinia can result in a bloodstream infection.
In addition to the foregoing common causes of food-borne illnesses, certain others are tracked by the CDC, often because they can be deadly. Listeria is one such pathogen. Although only three persons in every one million persons get the disease, it is fatal in 25 percent of those infected and is especially harmful to fetuses. Listeria can survive refrigeration for weeks, but cooking kills the bacteria. Raw milk, undercooked or raw foods such as smoked salmon, and soft cheeses are the most common food sources. According to the CDC's data for 2013, Listeria is responsible for an estimated 260 deaths in the United States each year.
Treatment Initial treatment for persons with food-borne illnesses generally focuses on
rehydration, because both vomiting and diarrhea tend to lead to potentially
dangerous dehydration. Antibiotic therapy is necessary only in cases of invasive
bacterial infections, such as Shigella. In persons with mild to
moderate Salmonella infection, antibiotic therapy may not be
helpful and may actually be harmful; it can lead to the person being a long-term
asymptomatic carrier who can easily spread the bacteria to others.
Antibiotics should never be used for persons with suspected
STEC infection because of the increased risk for development of hemolytic-uremic
syndrome, which is fatal 5 to 10 percent of the time and leads to chronic kidney
disease in another 10 percent. Similarly, antibiotic therapy in persons with
C. difficile infection increases the risk of developing toxic
megacolon, with a 20 percent mortality rate. Antibiotic treatment is ineffective
in cases caused by viruses.
Risk Factors The risk factors associated with food-borne illnesses range from those at the kitchen level to those in the food system as a whole. Raw and undercooked foods, inadequate home canning, cross-contamination (in which bacteria is transmitted by, for example, the use of unwashed cutting boards), insufficient hygiene by food service workers, and foods kept at the wrong temperatures are all examples of risk factors at the consumer level.
At the producer level, food system issues include widespread consolidation, industrialization, and globalization, all risk factors for the spread of food-borne illnesses because they can lead to a lack of oversight and inspection and to problems with tracing foods that are produced on an industrial scale. For example, one infected cow can contaminate large amounts of ground beef because meat from many animals is often mixed during the processing of the ground beef.
Labor and economic development issues also can play a role in the spread of food-borne diseases. For example, a large percentage of fresh fruits and vegetables comes from countries without chlorinated water supplies. Contaminated water that is used to irrigate fields or wash produce after harvest can lead to Salmonella and E. coli infections inside the tissue of the produce itself, where it cannot be washed off. Farm workers, food service workers, and meat workers without appropriate access to toilets or facilities for handwashing can contaminate food too.
Industrial-scale, concentrated or confined animal-feeding operations (CAFOs)
are sources of nearly all the meat, poultry, and eggs in the United States. CAFOs
generate enormous amounts of animal waste, which is often disposed of by being
spread (as raw manure) on agricultural fields. Runoff from these fields can
contaminate drinking water. CAFOs are also blamed for increasing the development
of antibiotic-resistant bacteria by the routine use of low
doses of antibiotics in herds, which cause the animals to grow faster. The close
contact of thousands of confined animals also facilitates the spread of pathogens
among those animals.
Prevention and Outcomes In home kitchens, consumers can reduce their risk of food-borne illnesses by
practicing four principles of safe food handling: clean, separate, cook, and
chill. “Clean” means washing hands and food-preparation surfaces thoroughly and often.
“Separate” means keeping items that are used for animal products separate from
items used for other foods, and keeping animal products separate from other items
in one’s grocery cart, grocery bags, and refrigerator. “Cook” refers to cooking
foods to a high enough internal temperature to kill pathogens and staying away
from raw or partially cooked foods, such as rare steaks or sauces containing raw
eggs. “Chill” refers to refrigerating leftover food promptly in a refrigerator
kept at 40° Fahrenheit or lower. Consumers should also practice the so-called
2-2-4 rule for safe handling of leftovers: no more than two hours should pass
between cooking the food and refrigerating leftovers; store food in shallow
containers (no more than two inches deep) so it cools quickly once refrigerated;
and use or freeze the food within four days.
Consumers also can reduce their food-borne disease risk through their food choices. Avoiding or minimizing consumption of animal products is one way to minimize risk, as meat, poultry, seafood, eggs, and dairy are the primary sources of food-borne diseases in the United States. Free-range eggs are less likely to carry Salmonella than are eggs from hens kept in battery cages, and organic eggs are even safer than free-range eggs. Meat and poultry from animals raised on smaller farms, on pasture, and (for cattle) on eating grass rather than corn is less likely than factory-farmed meat and poultry to carry E. coli and other pathogens.
Only one-quarter of food-borne illnesses originate from improper home food-handling, with the remainder caused by problems at the source or somewhere along the chain before food reaches the eater. Regulatory oversight of food in the United States is fragmented among multiple departments and agencies. The US Department of Agriculture (USDA) inspects meat, poultry, and pasteurized and processed eggs, whereas the US Food and Drug Administration (FDA) regulates all other foods. Regulatory fragmentation and resource and budget constraints on inspection processes may be further systemic causes of the ongoing problems related to food safety in the United States.
Impact In 2015, the CDC estimated, according to data from 2011, that food-borne illnesses are responsible for at least 48 million illnesses, 128,000 hospitalizations, and 3,000 deaths in the United States each year. About one in six Americans becomes sick after eating contaminated foods or drinking contaminated beverages every year. As of 2015, the CDC reported 250 different food-borne diseases.
Food-borne illnesses cost the US economy billions of dollars each year. Costs are incurred by patients and the health care system for treatment. Patients may lose wages, and their illnesses are a drain on productivity. According to a 2014 report from the USDA's Economic Research Service, food-borne illnesses were costing more than $15.6 billion annually.
Outbreaks also lead to food recalls and associated costs. For example, in 2008, Westland/Hallmark recalled more than 143 million pounds of beef after the USDA deemed the beef unfit for human consumption. In 2009, the Peanut Corporation of America recalled more than 3,900 different bulk peanut-butter products from roughly 360 different companies because of suspected Salmonella contamination. The USDA reported fifty-two recalls of meat contaminated with E. coli O157:H7 between 2007 and 2009. In addition, food-borne illnesses also lead to an intangible cost: the loss of trust in the food system. In a 2009 survey, less than 20 percent of respondents said they trusted food companies to develop and sell safe foods.
In late 2015, two outbreaks of food-borne illness severely damaged the reputation of popular nationwide restaurant Chipotle. After the CDC linked more than fifty cases of E. coli STEC O26 to food served at several of the chain's restaurants in nine states throughout the country, questions were raised once again about the lack of understanding regarding food-borne illness and food safety, especially because of Chipotle's dedication to using fresh and organic products. The concern was further heightened when a second outbreak occurred at a Chipotle in Boston that left several Boston College students ill with norovirus.
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