ERS estimates US foodborne disease costs - Economic Research Service - includes related articles

Microbial pathogens in food cause between 6.5 million and 33 million cases of human illness and up to 9,000 deaths each year in the United States. Over 40 different foodborne pathogens are believed to cause human illness. The annual cost of human illness caused by seven foodborne pathogens for which we have estimates ranges between $5.6 billion and $9.4 billion. Meat and poultry are the primary sources.

Microorganisms are commonly found in soil, water, plants, and animals. Most do not cause human illness. In fact, we rely on some microorganisms in the making of bread, alcohol, cheese, vitamins, and antibiotics.

Some, however, do cause human illness. Pathogens - microorganisms that cause disease - include viruses, bacteria, parasites, and fungi. The bacterium Staphylococcus aureus lives harmlessly on human skin and in the nasal cavities of less than half the people in the United States, but in food it can produce toxins that cause human illness. Another bacterium Escherichia coli O157:H7 usually lives harmlessly in the intestinal tracts of some cattle, but in people it can cause serious illness, including bloody diarrhea and kidney failure, as well as premature death. People can acquire the bacteria by eating mishandled or insufficiently cooked meat from infected animals. Half of all foodborne illnesses have no identified cause. Yet of those foodborne illnesses that are confirmed and reported to the Centers for Disease Control and Prevention (CDC), over 90 percent are attributed to bacteria.

Increasing Government scrutiny over food safety is improving efforts to restrict microbial pathogens in the food supply - as well as to improve data on the numbers of cases and costs associated with these pathogens. This article is the first in a new Economic Research Service series that will track the estimated costs and incidence of seven foodborne diseases over time (see box on key foodborne pathogens). These diseases were chosen for this series because they are commonly found in meat and poultry.

Public-health officials can compare the cost-of-illness (COI) estimates to identify the most expensive foodborne pathogens and illnesses. COI estimates can also be compared with the costs of pathogen-control programs to determine what level and direction of intervention may be needed.

Foods Contain Pathogens

Foods are the major source for some pathogens, such as Listeria monocytogenes, E. coli O157:H7, Salmonella, and Campylobacter jejuni (table 1). People also can be exposed to pathogens through inhalation, by drinking contaminated water, and by contact with infected pets, farm animals, and people.

Foods most likely to carry pathogens are high-protein, nonacid foods, such as meat, poultry, seafood, dairy products, and eggs (see box on sources of pathogens). Farm livestock and poultry infected with microbial pathogens may expose other animals in a herd or flock by excreting pathogens, pathogen cysts, or larvae.

However, for most pathogens commonly found on meat and poultry flesh, contamination does not usually occur until slaughter. Slaughtering, defeathering, chilling, and processing stages all provide opportunities for contamination. Accidental puncturing of the intestinal tract during slaughter can lead to widespread contamination of a packing line. Proper sanitation on the farm, in fishing vessels, and in processing plants can reduce the pathogen level on food that goes to retail. Animal products, such as milk and eggs, also require proper handling.

Consumers can reduce their risks from foodborne illness by: cooking foods thoroughly; practicing sanitary kitchen techniques, such as washing utensils and cutting boards that came in contact with raw meat; immediately refrigerating and properly packaging leftover foods; and not consuming unpasteurized milk, and raw or rare meat, poultry, eggs, or seafood. However, consumers cannot protect themselves from all microbial hazards. Some pathogens are not easily killed by cooking or by refrigeration. For instance, if meat and poultry are contaminated with Staphylococcus aureus and are held at unsafe temperatures, S. aureus can produce heat-stable toxins that are able to withstand temperatures as high as 250 [degrees] F. Listeria can survive and multiply during refrigeration.

Severity of Foodborne Illness Varies

Microbial pathogens in food can cause infections when the pathogens are eaten and are then established in the body, usually multiplying inside human intestinal tracts, and irritating the lining of the intestines. Two pathogens that cause infections are Listeria and Campylobacter. Sometimes these pathogens invade other tissues, causing additional infections.

Other microbial pathogens when eaten in food may produce harmful or deadly toxins while growing in the human intestinal tract. These toxic byproducts - not the pathogens themselves - cause human illness. Two pathogens that cause this kind of foodborne illness are Clostridium perfringens and E. coli O157:H7.

Human illness from microbial pathogens can also occur when someone consumes food tainted with either toxins released during the growth stages of specific bacteria (such as Staphylococcus aureus) or mycotoxins produced by molds. Illnesses from these sources tend to occur quickly after consumption, because they do not involve any establishment or growth stage in the human body.

Four main categories of factors increase the risk and severity of a foodborne illness:

* Microbial factors, such as the type, strain, and quantity of pathogens or toxins ingested;

* Host factors, such as an individual's age, stress level, and strength of immune system;

* Diet-related factors, such as nutritional deficiencies; and

* Other factors, such as the geographical distribution of pathogens in soil and water.

Researchers are gaining greater knowledge of how these factors place people at greater risk for some pathogens. For example, high levels of iron in a person's blood can increase the risk of illness from ingesting Vibrio vulnificus, a deadly seafood pathogen. Some pathogens require ingestion of only very small amounts of a pathogen, or its cysts or larvae, to result in infectious illness. Ingestion of only one cyst, for example, can result in toxoplasmosis.

Most cases of foodborne illness are classified as "acute." These are usually self-limiting and of short duration, although they can range from mild to severe. Gastrointestinal problems and vomiting are common acute symptoms of many foodborne illnesses. Deaths from acute foodborne illnesses are uncommon and more typically occur in the very young, elderly, or patients with compromised immune systems (such as those suffering from AIDS and cancer). However, the U.S. Food and Drug Administration (FDA) estimates that 2 to 3 percent of all acute cases develop secondary long-term illnesses, called "chronic sequelae," such as arthritis.

Chronic sequelae of foodborne illness can occur in any part of the body and subsequently affect the joints, nervous system, kidneys, or heart. These chronic illnesses may afflict the patients for the remainder of their lives or result in premature death. For example, Campylobacter infections are estimated to be responsible for 20 to 40 percent of Guillain-Barre syndrome cases (a major cause of paralysis unrelated to [TABULAR DATA FOR TABLE 1 OMITTED] trauma) in the United States. About 5 percent of E. coli O157:H7 disease patients develop hemolytic uremic syndrome, which usually involves red blood cell destruction, kidney failure, and neurological complications, such as seizures and strokes.

Animal Products Are Major Sources of Illness-Causing Pathogens(1)

Bean, N.H., P.M. Griffin, J.S. Goulding, and C.B. Ivey. "Foodborne Disease Outbreaks, 5 Year Summary, 1983-1987," CDC Surveillance Summary Morbidity Mortality Weekly Report. Vol. 39, Issue SS-1, 1990, pp. 15-59.

Control of Communicable Diseases in Man, 15th edition, Abram S. Benenson, Ed. Washington, DC: American Public Health Association, 1990.

Foodborne Pathogens: Risks and Consequences, Task Force Report, No. 122. Washington, DC: Council for Agricultural Science and Technology, Sept. 1994.

"Preliminary Regulatory Impact Assessment for Docket No. 93-016P - Pathogen Reduction; Hazard Analysis and Critical Control Point (HACCP) Systems," Federal Register, Vol. 60, No. 23, Feb. 3, 1995, pp. 6774-889.

Tappero, J.W., A. Schuchat, K.A. Deaver, L. Mascola, and J.D. Wenger. "Reduction in the Incidence of Human Listeriosis in the United States," Journal of the American Medical Association, Vol. 273, Issue 14, Ap. 12, 1995, pp. 1118-22.

RELATED ARTICLE: Seven Key Foodborne Pathogens Causing Human Illnesses in the United States

* Symptoms from Campylobacter jejuni infections range from a mild illness with diarrhea lasting a day, to severe abdominal pain, severe diarrhea (sometimes bloody), sometimes accompanied by fever, occasionally lasting for several weeks. The incubation period for most cases is 2-5 days and the illness usually lasts from 2 to 10 days, depending on its severity. Although the illness is generally regarded as a relatively mild disease, death can occur in some cases, especially for the very young, very old, or immunocompromised.

* Illness from Clostridium perfringens intoxications typically occurs 6 to 24 hours after ingestion of food bearing large counts of this bacteria. The illness in humans is frequently a mild gastrointestinal distress, lasting only around a day. Deaths are uncommon.

* Escherichia coli O157:H7 disease is usually a mild gastrointestinal illness that occurs 3 to 5 days after eating contaminated food. However, E. coli O157:H7 disease can result in illness requiring hospitalization: hemorrhagic colitis and hemolytic uremic syndrome (HUS). Hemorrhagic colitis is distinguished by the sudden onset of severe abdominal cramps, little or no fever, and diarrhea that may become grossly bloody. Although less than 5 percent of E. coli O157:H7 disease cases develop HUS, it is a severe, life-threatening illness. HUS is a disease characterized by red blood cell destruction, kidney failure, and neurological complications, such as seizures and strokes. Most of these HUS cases are children under 5 years old, although the feeble elderly may also be at risk.

* Illness caused by the bacterium Listeria monocytogenes may be either mild or severe. Milder cases are characterized by a sudden onset of fever, severe headache, vomiting, and other influenza-type symptoms. Severe cases can result in chronic illness and death. Listeriosis may appear mild in healthy adults and more severe in fetuses, the elderly, and the immunocompromised. Outbreak data show that the incubation period ranges from 3 to 70 days.

* Illness from the bacterium Salmonella usually appears 6 to 74 hours after eating contaminated food and lasts for a day or two. Common symptoms are nausea, diarrhea, stomach pain, and sometimes vomiting. In rare cases Salmonella, like many other bacterial and parasitic infections, can cause chronic disease syndromes such as arthritis and meningitis. Although the illness is generally regarded as a relatively mild disease, death can occur in some cases - specially for the very young, very old, or immunocompromised.

* Staphylococcus aureus intoxications occur usually within 1 to 6 hours following consumption of the toxins produced by the bacteria. In fact, onset of symptoms may occur within 30 minutes of consumption. Illness caused by S. aureus enterotoxin is characterized by severe nausea, vomiting, cramps, and diarrhea. Although the illness generally does not last longer than 1 or 2 days, the severity of the illness may indicate the need for hospitalization and possibly for surgical exploration.

* Toxoplasma gondii is a parasite that can cause acute or chronic human illness when people eat undercooked pork, mutton, and some other meats. The acute illness has mild flu-like symptoms. People can also be exposed to T. gondii through contact with cats or cat excrement. Most people infected with the parasite do not have any symptoms, and some people are at higher risk of getting sick from this parasite. Women infected with T. gondii during pregnancy may transmit the infection to their fetus, possibly leading to still-births or babies born with birth defects ranging from hearing or visual impairments to mental retardation. People with suppressed immune systems, such as AIDS and cancer patients, are also at higher risk than others from this parasite. One outbreak associated with undercooked meat indicates that the incubation period ranges from 10 to 23 days.

Buzby is an agricultural economist with the University of Kentucky, stationed at the Food and Consumer Economics Division, Economic Research Service, USDA. Roberts is an economist, also with the Food and Consumer Economics Division.

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