Food Safety Agencies Introduce New Model to Better Identify Foodborne Illness Sources

FDA, CDC and the USDA’s FSIS have jointly released a report on the new method for analyzing outbreak data to identify better foods that are responsible for illness related to four major foodborne bacteria.

Titled “Foodborne Illness Source Attribution Estimates forSalmonella, Escherichia coli O157 (E. coliO157), Listeria monocytogenes (Lm), and Campylobacter using Outbreak Surveillance Data,” the report was produced by the Interagency Food Safety Analytics Collaboration (IFSAC).

FSTNewsNewModelforOutbreaks For the new model, IFSAC analyzed data from nearly 1,000 outbreaks that occurred between 1998 and 2012, excluding those that involved multiple pathogens, those for which no food vehicle was identified, and those attributed to food containing multiple ingredients, to assess which categories of foods were most responsible for making people sick with Salmonella, E. coli O157, Listeria, and Campylobacter.

The pathogens were chosen because of the frequency or severity of the illnesses they cause, and because targeted interventions can have a significant impact in reducing them. Some of the findings include:

  • More than 80 percent of E. coli O157 illnesses were attributed to beef and vegetable row crops, such as leafy vegetables.
  • Salmonella illnesses were broadly attributed across food commodities, with 77 percent of illnesses related to seeded vegetables (such as tomatoes), eggs, fruits, chicken, beef, sprouts and pork.
  • Nearly 75 percent of Campylobacter illnesses were attributed to dairy (66 percent) and chicken (8 percent). Most of the dairy outbreaks used in the analysis were related to raw milk or cheese produced from raw milk, such as unpasteurized queso fresco.
  • More than 80 percent of Listeria illnesses were attributed to fruit (50 percent) and dairy (31 percent). Data were sparse for Listeria, and the estimate for fruit reflects the impact of a single large outbreak linked to cantaloupes in 2011.

The new model using data from the resulting 952 outbreaks differs from previous methods by using a categorization of foods updated to align with the regulatory framework of FDA and FSIS. The model focuses more on recent outbreaks by giving less weight to data from 1998 through 2007, and decreasing the bias that potentially results from very large outbreaks.

“This suggests interventions designed to reduce foodborne salmonellosis need to include a variety of approaches,” IFSAC’s report states. “For [Listeria monocytogenes], the limited number of outbreaks and wide credibility intervals dictate caution in interpreting the attribution percentages for fruit and dairy,” the report notes.

The report also noted that “Lm outbreaks have been frequently linked to the Dairy category, specifically with the consumption of soft cheeses by pregnant women and persons with weakened immune systems. Although the wide credibility interval for the Fruit category substantially limits interpretation, the analysis does suggest vigilance in seeking unrecognized sources of outbreaks and illnesses in this food category.”

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