Appendix A: Evaluation of food-borne enteric illness prevention, detection and response activities at the Public Health Agency – Centre for Disease Control

Appendix A: The United States Centers for Disease Control and Prevention (CDC)


Tracking single cases of food-borne illness and investigating outbreaks are critical public health functions for the Centers for Disease Control and Prevention (CDC), which estimates that each year, food-borne diseases cause illness in one in six Americans (or about 48 million people) resulting in 128,000 hospitalizations and 3,000 deaths.Footnote 72

In 2010, the CDC monitored between 17 and 42 potential food poisoning clusters per week and investigated more than 2,000 multistate clusters.Footnote 73

Local and state health departments are responsible for the investigation of food-borne outbreaks, but the CDC does provide consultation on some of those, as well as assistance on requests for outbreaks that are particularly large, unusual, or severe.Footnote 74

The Department of Health and Human Services at CDC works with a number of public health partners, including state, county, and city health departments, and the federal regulatory agencies, such as the United States Food and Drug Administration and the Food Safety and Inspection Service of the United States Department of Agriculture. During a multistate outbreak, the CDC serves as lead coordinator between public health partners to detect the outbreak, define its size and extent, and to identify the source.Footnote 75Footnote 76

The Food and Drug Administration

The Food and Drug Administration aims to protect public health by ensuring that the food supply is safe. The Food and Drug Administration regulates all foods, except for raw meat, poultry and certain egg products, and its involvement in an outbreak investigation begins when a Food and Drug Administration-regulated product is suspected as the potential source of the outbreak. The Food and Drug Administration then alerts the public by issuing a recall of the suspected product, monitors the recall and identifies how the food became contaminated.Footnote 77Footnote 78

The United States Department of Agriculture

The United States Department of Agriculture sets federal policies regarding food safety and agricultural concern and is responsible for agriculture, food and nutrition, working with the Food and Drug Administration to address food safety and to provide consumer resources.Footnote 79 Footnote 80

Policies and legislation

On January 4, 2011, the FDA Food Safety Modernization Act was signed into law. The Act focuses on three theme areas: improving capacity to prevent food safety problems; improving capacity to detect and respond to food safety problems; and improving the safety of imported food.Footnote 81

The FDA Food Safety Modernization Act is focussed on conferring more authority to the Food and Drug Administration for areas such as increasing inspection and safety standards. The Food and Drug Administration has the authority to issue a mandatory recall of products if a company fails to voluntarily withdraw its own product(s). There are a number of provisions for public health, such as increasing training and creating Centers of Excellence. However, no new funds were provided to the CDC to undertake these activities.Footnote 82

Does the CDC have a role in preventing food-borne illness?

The Enteric Diseases Epidemiology Branch is the CDC’s lead epidemiology and surveillance group;Footnote 83 it focuses its work on determining causes of food-borne illness. As noted by a key informant, although the Branch is interested in food safety issues at the farm level, this is not its mandate. The CDC’s mission is to address human health. They use, among others, two key tools for that purpose.


Firstly, the Foodborne Diseases Active Surveillance Network (FoodNet) was established in 1995 to conduct surveillance of specific food-borne pathogens, such as E. coli O157/non O157 and Salmonella, through laboratory testing of samples from patients.

It is a collaborative program among the CDC, 10 state health departments, the Department of Agriculture’s Food Safety and Inspection Service and the Food and Drug Administration. It covers an estimated 15 per cent of the United States population (46 million persons).Footnote 84

FoodNet is different from other food-borne disease surveillance systems because it does not rely on reporting of food-borne diseases by clinical laboratories to state health departments, which in turn report to CDC; it is instead an active surveillance system, meaning that public health officials frequently contact laboratory directors to find new cases of food-borne illnesses and report these cases electronically directly to the CDC.Footnote 85


Secondly, the National Antimicrobial Resistance Monitoring System (NARMS) collects information on antimicrobial resistance in food-borne bacteria in humans. It is a collaborative effort between the CDC, the Food and Drug Administration (Center for Veterinary Medicine) and the Department of Agriculture (Food Safety and Inspection Service and Agricultural Research Services).Footnote 86

NARMS data have been collected since 1996, thereby making trend analysis possible, including information about patterns of emerging resistance.Footnote 87

Evidence produced by the CDC from these sources and other investigations has been used to change the food safety system.

  • The CDC/State investigative information demonstrated a link between Salmonella and shell eggs. The Food and Drug Administration developed the Egg Safety Final Rule regulations (2009) for egg farms with 3,000 or more laying hens.
  • NARMS data demonstrated an increase in antibiotic resistant human illness from poultry consumption. The Food and Drug Administration withdrew the approved use of Enrofloxacin (an antibiotic) for use in poultry.Footnote 88

What are CDC’s detection activities?

The Enteric Diseases Laboratory Branch is the CDC’s lead group for the use of molecular subtyping in the national and international surveillance of food-borne infections. Its activities include:

  • Managing PulseNet, a network designed to help all states to detect, investigate and control outbreaks
  • Partnering with reference laboratories throughout the world
  • Building capacity for molecular surveillance of food-borne infections.Footnote 89

PulseNet is a network of national and global public health and food regulatory agency laboratories that share standardized methods of DNA fingerprinting of food-borne disease-causing bacteria by pulsed-field gel electrophoresis (PFGE). PFGE can be used to distinguish strains of organisms such as Escherichia coli O157:H7, Salmonella, Shigella, Listeria, or Campylobacter at the DNA level. DNA “fingerprints,” or patterns, are then submitted electronically to a dynamic database at the CDC allowing for rapid comparison of the patterns.Footnote 90

PulseNet allows for real-time communication among state and local health departments and international partners, and for investigators to find similar patterns, thus making it easier to determine whether an outbreak is occurring, even if the affected persons are geographically far apart. As a result, clusters of outbreaks and their causes can be identified in a matter of hours rather than days.Footnote 91

How does the CDC respond to food-borne illness?

The CDC’s Outbreak Response and Prevention Branch is responsible for ensuring rapid and coordinated surveillance for the detection and response to multistate outbreaks of food-borne disease.Footnote 92

The Foodborne Diseases Centers for Outbreak Response Enhancement (FoodCORE) is a CDC funded project to improve state and local responses to food-borne disease outbreaks. Sites were developed to create new and better methods to detect, investigate, respond to, and control multistate outbreaks of food-borne diseases. Currently, seven sites participate in FoodCORE, and since capacity varies from state to state, it is designed to provide resources to assist the funded states.Footnote 93

The majority of the Outbreak Response and Prevention Branch’s work is in the area of outbreak response. Like Canada, jurisdiction for a food-borne enteric illness investigation rests with the state and local health departments. Therefore, when a cluster is detected, primarily through PulseNet, the CDC works with the affected state in the response. If there are a number of cases in one particular state, the CDC will ask that state if it has undertaken an investigation, and if so, whether that state wishes to lead the investigation or let the CDC take leadership. The CDC will also organize a response if more than one state is involved and will work with other food safety partners (such as the Food and Drug Administration and the Food Safety and Inspection Service) to ensure a coordinated response.

The Outbreak Response and Prevention Branch has two mechanisms in place for surge capacity: the Epidemic Intelligence Service (EIS) program and activation of the Emergency Operations Center. The Epidemic Intelligence Service program is a two-year postgraduate epidemiology training program, with approximately 13 EIS officers who can be deployed to help with local surge capacity at the request of states.

For the epidemiological investigations’ case control studies, the Emergency Operations Center will be activated with a call going out for volunteers who possess a public health background, and who will receive additional training to prepare for the calls. In addition, Emery University has a Student Outbreak Response Team of approximately 30 students that can be called upon to volunteer for the call center. One key informant noted that approximately 8,000 – 10,000 calls can be made in one night.

Building capacity

The CDC builds capacity through the following funding mechanisms: the Epidemiology and Laboratory Capacity for Infectious Diseases (ELC) Funding and the Emerging Infections Programs (EIP) Funding. The ELC strives to build and improve state health department workforces, training, and tools necessary to rapidly expand to meet healthcare-associated infections prevention efforts.Footnote 94 The EIP is a collaborative agreement “to assist in local, state, and national efforts to prevent, control, and assess the public health impact of emerging infectious diseases”.Footnote 95

What happens when outbreak response works well

Food-borne enteric illness outbreaks happen continuously but larger outbreaks with higher morbidity and mortality rates are less common. When these types of events occur, implementing plans, tools and strong coordination efforts are keys to success.

In 2011, cantaloupes contaminated with the bacteria Listeria monocytogenes caused the deadliest foodborne disease outbreak in the United States in nearly 90 years. The number of deaths would have been higher had it not been for an effective, coordinated response by the Centers for Disease Control and Prevention (CDC), state and local health departments, and the Food and Drug Administration (FDA).  Lives were saved because the outbreak was detected, its source was identified, and a national warning was issued – all in just a matter of days. Footnote 96

On average, Colorado reports two cases of Listeriosis annually for the month of August, but by September 2, 2011, the Colorado Department of Health and Environment had reported seven cases to the CDC. By September 6, 2011, the Colorado patients interviewed using the Listeria Initiative questionnaire reported that they had eaten cantaloupe in the month before they became ill.Footnote 97

The Listeria Initiative encourages states to interview all of their cases using a standard form. According to a key informant, having cantaloupe on the form was not due to a previous Listeriosis outbreak associated with cantaloupe, but because of a link that had been demonstrated over a dozen years ago in a FoodNet study. As a result, the Listeriosis investigative study was able to determine the source of the outbreak quickly. 

Because Colorado is part of FoodNet, the state already had good surveillance capacity and had already done the necessary basic surveillance work. Epidemiologists were quick to start interviewing those who became ill, with the key informant noting that the epidemiologists were able to draw on good relationships with the Department of Agriculture to inform them that they believed cantaloupe to be the source of the Listeriosis outbreak and ask them to collect samples. Five samples were collected from three different stores and in two of the three, all five cantaloupes came back positive for listeria. From there, the contaminated cantaloupes were traced back to a particular producer.

A number of factors led to the quick resolution to the outbreak and, although 84 persons became ill, resulting in 15 deaths, the outbreak could have been much worse if it had not been determined quickly that it was cantaloupes from a particular producer that were contaminated.

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