Chapter 2: Understanding How Food-borne Illnesses Are Tracked
- Return to Defending Claims.
In addition to understanding how our food is regulated, it is absolutely critical, when faced with a potential food-borne illness claim, to understand and appreciate how food-borne illnesses are identified, investigated and confirmed by relevant governmental public health agencies. Without this information, it will be virtually impossible to adequately defend any food-borne illness claim.
Indeed, to gain a better understanding of the extent of food-borne illness in America, the federal government in recent years has developed comprehensive initiatives to help federal, state and local governments identify, track and solve food-borne illness cases. In 1993, for instance, a large outbreak of food-borne illness caused by E. coli O157:H7 sickened more than a hundred people in the western United States. In this outbreak, pulsed-field gel electrophoresis (“PFGE”) was used to determine the source of the outbreak by matching the DNA of the implicated E. coli to hamburgers from a national restaurant chain.
In the years that followed the 1993 multi-state E. coli O157:H7 outbreak, numerous surveillance programs increased the federal government’s ability to detect food-borne illness cases on a national scale. Following the 1993 outbreaks, for example, the CDC created PulseNet so that scientists and public health laboratories throughout the country could upload and then rapidly compare the PFGE patterns of bacteria isolated from ill persons.
From 195 PFGE patterns in the mid-1990s, the database has grown to over 120,000 patterns today. All 50 state public health departments participate in PulseNet, along with several local public health laboratories and the USDA and FDA. PulseNet Canada and PulseNet USA exchange DNA fingerprints and associated information in real time. Having real-time access to such information has helped investigators determine: (1) whether reported food-borne illness cases are genetically similar; and (2) whether they likely originated from a common source. Today, PulseNet links the CDC, state health departments, and food regulatory agencies so that multi-state outbreaks can be rapidly detected and investigated.
Bacterial pathogens analyzed include E. coli O157:H7, Listeria, Salmonella and other food-borne bacteria. When a PulseNet participating laboratory logs on to the PulseNet server, it will display a “recent match” message if two or more laboratories submit identical or closely related patterns within a specified time. A universal naming system was developed to help compare and interpret molecular subtyping information, using a 10-character code: XXXYYY.0000. The first three characters represent the bacterial pathogen, the next three denote the enzyme used for DNA restriction, and the last four characters represent the pattern designation. For example, in the pattern EXHA26.0026, EXH represents E. coli O157:H7, A26 represents restriction endonuclease AvrII, and 0026 is the pattern number.
Once a cluster of illnesses is identified that share a common PFGE pattern, epidemiologists interview patients in an effort to find or exclude a common source. Sources might be food, environmental elements or another person carrying and shedding the bacteria. The Outbreak Network for Food-borne Diseases Surveillance and Response, “OutbreakNet,” is a network of public health epidemiologists at the local, state and federal level who investigate food-borne and diarrheal disease outbreaks. OutbreakNet participants use standardized interview methods and forms, seeking to assess whether there are statistically significant common exposures among the patients. Information is shared rapidly via email, conference calls and website postings, and updated constantly during outbreaks so that if a common source can be identified, corrective action can be taken to minimize further illnesses.
An example of multi-state sharing among epidemiologists is this email from a recent outbreak suspected to be associated with ground beef:
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The third part of the CDC surveillance network is The Food-borne Diseases Active Surveillance Network, “FoodNet,” which compiles evidence to draw broader conclusions about the extent of food-borne illnesses. FoodNet is a collaborative project of the CDC, 10 states (California, Colorado, Connecticut, Georgia, Maryland, Minnesota, New Mexico, New York, Oregon and Tennessee), the USDA, and the FDA. This network collects data regarding diseases caused by enteric pathogens transmitted commonly through food. FoodNet staff routinely contact all clinical laboratories in the 10 FoodNet sites to collect information on every laboratory-confirmed case under surveillance. FoodNet surveillance in the 10 participating states includes nearly 45 million people, or approximately 15% of the United States’ population. For 2006, FoodNet reported rates of infection per 100,000 people as follows:
- Salmonella: 14.81
- Campylobacter: 12.71
- Shigella: 6.09
- Cryptosporidium: 1.91
- E. coli O157:H7: 1.31
- non-O157:H7 STEC: .46
- Yersinia: .35
- Vibrio: .34
- Listeria: .31
- Clycolspora: .09
FoodNet also estimates the burden and trends over time for food-borne infections, and conducts studies to better understand the epidemiology of food-borne diseases. Its goal is to develop better prevention strategies at each step of the farm-to-table continuum so as to reduce the burden of food-borne illness. Proper handling at each step, including food preparation, is always stressed.
Aided by new initiatives such as PulseNet, OutbreakNet and FoodNet, the CDC estimates that, annually, nearly 76 million people continue to be affected by some type of food-borne illness. Of these, more than 300,000 are hospitalized and about 6,000 people die. Although most people affected by food-borne illness develop only mild symptoms (or remain asymptomatic), food-born illness can cause greater concern for those with compromised or weakened immune systems, such as the very young or old. Because food-borne pathogens continue to exist naturally in many raw foods such as raw meat and poultry, and because there is no technology to eliminate them during production (with the exception, of course, of irradiation or cooking), today’s challenges with respect to the food supply remain as real as they are complex. As consumers, we must individually take care to avoid the potential hazards associated with raw foods. As industry representatives, insurers and lawyers, we must remain cognizant of the role food-borne illness will likely continue to play in our professional disciplines.
In any event, as food safety lawyers, it is and will always remain critical to be intimately familiar with these and other surveillance programs, and to stay abreast of new developments. Indeed, as surveillance continues to improve, the number of illness identified, and claims filed, will likely increase as well.
Copyright 2009 by Shawn K. Stevens
