The Centers for Disease Control and Prevention (CDC) in the Department of Health and Human Services is the federal agency primarily responsible for monitoring the incidence of foodborne illness in the United States. In collaboration with state and local health departments and other federal agencies, CDC investigates outbreaks of foodborne illnesses and supports disease surveillance, research, prevention efforts, and training related to foodborne illnesses. CDC coordinates its activities concerning the safety of the food supply with the Food and Drug Administration (FDA), which is also in the Department of Health and Human Services. With respect to the safety of meat, poultry, and eggs, CDC coordinates with the Food Safety and Inspection Service (FSIS) in the U.S. Department of Agriculture (USDA). CDC monitors individual cases of illness from harmful bacteria, viruses, chemicals, and parasites (hereafter referred to collectively as pathogens) that are known to be transmitted by foods, as well as foodborne outbreaks, through voluntary reports from state and local health departments, FDA, and FSIS. In practice, because CDC does not have the authority to require states to report data on foodborne illnesses, each state determines which diseases it will report to CDC. In addition, state laboratories voluntarily report the number of positive test results for several diseases that CDC has chosen to monitor. However, these reports do not identify the source of infection and are not limited to cases of foodborne illness. CDC also investigates a limited number of more severe or unusual outbreaks when state authorities request assistance. At least 30 pathogens are associated with foodborne illnesses. For reporting purposes, CDC categorizes the causes of outbreaks of foodborne illnesses as bacterial, chemical, viral, parasitic, or unknown pathogens. Although many people associate foodborne illnesses primarily with meat, poultry, eggs, and seafood products, many other foods—including milk, cheese, ice cream, orange and apple juices, cantaloupes, and vegetables—have also been involved in outbreaks during the last decade. Bacterial pathogens are the most commonly identified cause of outbreaks of foodborne illnesses. Bacterial pathogens can be easily transmitted and can multiply rapidly in food, making them difficult to control. CDC has targeted four of them—E. coli O157:H7, Salmonella Enteritidis, Listeria monocytogenes, and Campylobacter jejuni—as being of greatest concern. The existing data on foodborne illnesses have weaknesses and may not fully depict the extent of the problem. In particular, public health experts believe that the majority of cases of foodborne illness are not reported because the initial symptoms of most foodborne illnesses are not severe enough to warrant medical attention, the medical facility or state does not report such cases, or the illness is not recognized as foodborne. However, according to the best available estimates, based largely on CDC’s data, millions of people become sick from contaminated food each year, and several thousand die. In addition, public health and food safety officials believe that the risk of foodborne illnesses is increasing for several reasons. Between 6.5 million and 81 million cases of foodborne illness and as many as 9,100 related deaths occur each year, according to the estimates provided by several studies conducted over the past 10 years. The wide range in the estimated number of foodborne illnesses and related deaths is due primarily to the considerable uncertainty about the number of cases that are never reported to CDC. For example, CDC officials believe that many intestinal illnesses that are commonly referred to as the stomach flu are caused by foodborne pathogens. People do not usually associate these illnesses with food because the onset of symptoms occurs 2 or more days after the contaminated food was eaten. Furthermore, most physicians and health professionals treat patients who have diarrhea without ever identifying the specific cause of the illness. In severe or persistent cases, a laboratory test may be ordered to identify the responsible pathogen. Finally, physicians may not associate the symptoms they observe with a pathogen that they are required to report to the state or local health authorities. For example, a CDC official cited a Nevada outbreak in which no illnesses from E. coli O157:H7 had been reported to health officials, despite a requirement that physicians report such cases to the state health department. Nevertheless, 58 illnesses from this outbreak were subsequently identified. In the absence of more complete reporting, researchers can only broadly estimate the number of illnesses and related deaths. Food safety and public health officials believe that several factors are contributing to an increased risk of foodborne illnesses. First, the food supply is changing in ways that can promote foodborne illnesses. For example, as a result of modern animal husbandry techniques, such as crowding a large number of animals together, the pathogens that can cause foodborne illnesses in humans can spread throughout the herd. Also, because of broad distribution, contaminated food products can reach more people in more locations. Subsequent mishandling can further compound the problem. For example, leaving perishable food at room temperature increases the likelihood of bacterial growth and undercooking reduces the likelihood that bacteria will be killed. Knowledgeable experts believe that although illnesses and deaths often result from improper handling and preparation, the pathogens were, in many cases, already present at the processing stage. Second, because of demographic changes, more people are at greater risk of contracting a foodborne illness. In particular, certain populations are at greater risk for these illnesses: people with suppressed immune systems, children in group settings like daycare, and the elderly. Third, three of the four pathogens CDC considers the most important were unrecognized as causes of foodborne illness 20 years ago—Campylobacter, Listeria, and E. coli O157:H7. Fourth, bacteria already recognized as sources of foodborne illnesses have found new modes of transmission. While many illnesses from E. coli O157:H7 occur from eating insufficiently cooked hamburger, these bacteria have also been found more recently in other foods, such as salami, raw milk, apple cider, and lettuce. Fifth, some pathogens are far more resistant than expected to long-standing food-processing and storage techniques previously believed to provide some protection against the growth of bacteria. For example, some bacterial pathogens (such as Yersinia and Listeria) can continue to grow in food under refrigeration. Finally, according to CDC officials, virulent strains of well-known bacteria have continued to emerge. For example, one such pathogen, E. coli O104:H21, is another potentially deadly strain of E. coli. In 1994, CDC found this new strain in milk from a Montana dairy. While foodborne illnesses are often temporary, they can also result in more serious illnesses requiring hospitalization, long-term disability, and death. Although the overall cost of foodborne illnesses is not known, two recent USDA estimates place some of the costs in the range of $5.6 billion to more than $22 billion per year. The first estimate, covering only the portion related to the medical costs and productivity losses of seven specific pathogens, places the costs in the range of $5.6 billion to $9.4 billion. The second, covering only the value of avoiding deaths from five specific pathogens, places the costs in the range of $6.6 billion to $22 billion. Although often mild, foodborne illnesses can lead to more serious illnesses and death. For example, in a small percentage of cases, foodborne infections can spread through the bloodstream to other organs, resulting in serious long-term disability or death. Serious complications can also result when diarrhetic infections resulting from foodborne pathogens act as a triggering mechanism in susceptible individuals, causing an illness such as reactive arthritis to flare up. In other cases, no immediate symptoms may appear, but serious consequences may eventually develop. The likelihood of serious complications is unknown, but some experts estimate that about 2 to 3 percent of all cases of foodborne illness lead to serious consequences. For example: E. coli O157:H7 can cause kidney failure in young children and infants and is most commonly transmitted to humans through the consumption of undercooked ground beef. The largest reported outbreak in North America occurred in 1993 and affected over 700 people, including many children who ate undercooked hamburgers at a fast food restaurant chain. Fifty-five patients, including four children who died, developed a severe disease, Hemolytic Uremic Syndrome, which is characterized by kidney failure. Salmonella can lead to reactive arthritis, serious infections, and deaths. In recent years, outbreaks have been caused by the consumption of many different foods of animal origin, including beef, poultry, eggs, milk and dairy products, and pork. The largest outbreak, occurring in the Chicago area in 1985, involved over 16,000 laboratory-confirmed cases and an estimated 200,000 total cases. Some of these cases resulted in reactive arthritis. For example, one institution that treated 565 patients from this outbreak confirmed that 13 patients had developed reactive arthritis after consuming contaminated milk. In addition, 14 deaths may have been associated with this outbreak. Listeria can cause meningitis and stillbirths and is fatal in 20 to 40 percent of cases. All foods may contain these bacteria, particularly poultry and dairy products. Illnesses from this pathogen occur mostly in single cases rather than in outbreaks. The largest outbreak in North America occurred in 1985 in Los Angeles, largely in pregnant women and their fetuses. More than 140 cases of illness were reported, including at least 13 cases of meningitis. At least 48 deaths, including 20 stillbirths or miscarriages, were attributed to the outbreak. Soft cheese produced in a contaminated factory was confirmed as the source. Campylobacter may be the most common precipitating factor for Guillain-Barre syndrome, which is now one of the leading causes of paralysis from disease in the United States. Campylobacter infections occur in all age groups, with the greatest incidence in children under 1 year of age. The vast majority of cases occur individually, primarily from poultry, not during outbreaks.