IFSAC Projects

Overview of projects

The tri-agency collaborative identified four priority pathogens as the initial focus of their foodborne illness source attribution work:

• Salmonella,
• E. coli O157:H7,
• Listeria monocytogenes, and
• Campylobacter.

Based on the needs of each agency, CDC, FDA, and FSIS identified both short- and long-term needs related to foodborne illness source attribution, including:

• Short-term needs that focus on attribution estimates for the four priority pathogens; and
• Long-term needs that focus on plans for reducing uncertainty, improving data, and obtaining comprehensive estimates of foodborne illness source attribution.

Current projects

• Determining possible statistical modeling approaches to evaluate temporal changes in attribution estimates.
• Estimating food source attribution along the farm-to-table continuum.
• Reviewing existing body of work related to food source attribution for Campylobacter.
• Using Population Survey and Case Exposure Ascertainment data for food source attribution of Salmonella Enteritidis and Campylobacter illnesses.
• Exploring biases in foodborne illness outbreak reporting and its impact on disease attribution.

Completed projects

Developed a shared understanding and statement of needs for foodborne illness source attribution

• Objective: Through a series of discussions, accomplish the following goals:
  • Reach a shared understanding among the three agencies of historic and current methods and data sources used for foodborne illness source attribution.
  • Identify short- and long-term needs of IFSAC partners.
  • Review, compare, and select method(s) for estimating foodborne illness source attribution in the short term.
  • Develop plans for applying the method(s) to each prioritized pathogen.
• Project Results: During an April 2011 workshop held by the IFSAC Steering Committee and Technical Workgroup, team members developed a shared statement of needs and identified several analytic projects.

Improved food categorization scheme for attributing outbreaks and related illnesses to foods

• Objective: To expand the food categorization scheme used by CDC to classify foods implicated in foodborne disease outbreaks to include:
  • More specific food categories.
  • Useful categories for regulatory agencies and stakeholders.
• Project Results: Expanded the previously used food categorization scheme to include more specific food categories that:
  • Are more botanically correct.
  • Better reflect production practices and postharvest handling systems.
  • More readily distinguish FDA- and FSIS- regulated products.

After the updated scheme was determined, the IFSAC team assigned all applicable food items in the CDC outbreak surveillance database to these new categories. Additionally, the IFSAC team developed a food glossary with examples of foods for each food category.

The IFSAC food categorization scheme has five distinct levels to which foods can be assigned, depending upon the type of food. First, foods are assigned to one of four food groups (aquatic animals, land animals, plants, and other). Food groups include increasingly specific food categories; dairy, eggs, meat and poultry, and game are in the land animal food group, and the category meat and poultry is further subdivided into more specific categories of meat (beef, pork, other meat) and poultry (chicken, turkey, other poultry). Finally, foods are differentiated by differences in food processing (such as pasteurized fluid dairy products, unpasteurized fluid dairy products, pasteurized solid and semi-solid dairy products, and unpasteurized solid and semi-solid dairy products.

The IFSAC Food Categorization Scheme

IFSAC Food Categories with Examples

Estimated the proportion of SE illnesses attributable to shell eggs and other food categories

• Objective: To help assess the public health impact of the Egg Rule, an FDA regulation enacted in 2010 ("the Egg Rule"), this project sought to determine the proportion of illnesses attributable to shell eggs and other common sources before implementation of the rule.
• Project Results: Developed a new method to estimate the proportion of foodborne Salmonella serotype Enteritidis (SE) illnesses attributable to shell eggs and other major food commodity reservoirs of SE during the baseline period (2007-2009).

Among the included sources, shell eggs were estimated to be responsible for the highest proportion of foodborne SE infections (40%; 95% CI: 30-51%) during the baseline period (2007-2009). This estimate was required for the Department of Health and Human Services' FY14-15 Agency Priority goal, which was part of a government-wide Office of Management and Budget (OMB) performance management effort. This estimate will help improve our ability to assess the public health impact of the Egg Rule over time.

Compared characteristics of sporadic and outbreak-associated foodborne illnesses

• Objective: Investigate the representativeness of U.S. 2004-2011 outbreak illness data for making important inferences regarding the attribution for sporadic illnesses
• Project Results: Initial findings were shared during a January 2014 webinar. Final results were published in 2016 as a journal article, available on our IFSAC Publications page.

Applied models to estimate number of illnesses associated with foods and Salmonella subtypes

• Objective: Estimate the burden of human Salmonella infections attributable to specific food categories.
• Project Results: Findings were shared during a July 2015 presentation at the IAFP (International Association for Food Protection) Conference. A draft manuscript describing this completed work is in development.

Improved analyses of outbreak data used to assign implicated foods to food categories

• Objective: Determine analytic approach for attributing foodborne disease outbreaks to a single food source.
• Project Results: New food categories developed under this project are now incorporated into annual summaries of foodborne outbreaks and illnesses.

Communicated IFSAC activities and events to the public

• Objective: Communicating IFSAC activities, food safety interventions, and policies to the public and its stakeholders.
• Project Results: The IFSAC Communication Project entailed several deliverables:
  • First Public Meeting in January 2012
  • First webinar in June 2013 ("Improving the Categories Used to Classify Foods Implicated in Outbreaks.")
  • Second webinar in January 2014 ("Are Outbreak Illnesses Representative of Sporadic Illnesses?")
  • Development and launch of an IFSAC webpage in May 2014
  • Second Public Meeting in February 2015
  • Development of tri-agency approved press releases, Federal Register Notices (FRN), Constituent Updates, and a Key Messages document, among other communication documents.
  • Establishment of a permanent IFSAC Communication Workgroup; tasked with coordinating all IFSAC communication efforts

Developed a method for food source attribution for four bacteria using outbreak data

• Objective: Develop tri-agency outbreak-derived food source attribution fractions with quantified uncertainty bounds to use when attributing estimates for Salmonella, E. coli O157:H7, Listeria monocytogenes and Campylobacter.
• Project Results: A final report was publicly released in 2015, available on our IFSAC Publications page.

Developed a template for public communication of updated foodborne illness source attribution estimates for Salmonella, E. coli O157, Listeria monocytogenes, and Campylobacter.

• Objective: Development of a template for publicly providing updated foodborne illness source attribution estimates for Salmonella, Campylobacter, Escherichia coli (E. coli) O157, and Listeria monocytogenes using the most current tri-agency method for estimating attribution percentages from outbreak data.
• Project Results: IFSAC's annual estimates were first published in 2017, available on our IFSAC Annual Reports page.