Foodborne illness source attribution estimates for 2018 for Salmonella, Escherichia coli O157, Listeria monocytogenes, and Campylobacter using multi-year outbreak surveillance data, United States, December 2020

The U.S. Centers for Disease Control and Prevention reported in Dec.2020 that each year in the estimated 9 million people get sick, 56,000 are hospitalized, and 1,300 die of foodborne disease caused by known pathogens. These estimates help us understand the scope of this public health problem. However, to develop effective prevention measures, we need to understand the types of foods contributing to the problem.

The Interagency Food Safety Analytics Collaboration (IFSAC) is a tri-agency group created by the Centers for Disease Control and Prevention (CDC), the U.S. Food and Drug Administration (FDA), and the U.S. Department of Agriculture’s Food Safety and Inspection Service (USDA-FSIS). IFSAC developed a method to estimate the percentages of foodborne illness attributed to certain sources using outbreak data from 1998 through the most recent year for four priority pathogens: Salmonella, Escherichia coli O157, Listeria monocytogenes, and Campylobacter. IFSAC described this method and the estimates for 2012 in a report, peer-reviewed journal article, and at a public meeting. IFSAC derived the estimates for 2018 using the same method used for the 2012 estimates, with some modifications. The data came from 1,459 foodborne disease outbreaks that occurred from 1998 through 2018 and for which each confirmed or suspected implicated food was assigned to a single food category. The method relies most heavily on the most recent five years of outbreak data (2014 – 2018). Foods are categorized using a scheme IFSAC created that classifies foods into 17 categories that closely align with the U.S. food regulatory agencies’ classification needs. Salmonella illnesses came from a wide variety of foods.

More than 75% of Salmonella illnesses were attributed to seven food categories: Chicken, Seeded Vegetables (such as tomatoes), Pork, Fruits, Other Produce (such as nuts), Eggs and Turkey. E. coli O157 illnesses were most often linked to Vegetable Row Crops (such as leafy greens) and Beef. Over 75% of illnesses were linked to these two categories. Listeria monocytogenes illnesses were most often linked to Dairy products and Fruits. More than 75% of illnesses were attributed to these two categories, but the rarity of Listeria monocytogenes outbreaks makes these estimates less reliable than those for other pathogens. Non-Dairy Campylobacter illnesses were most often linked to Chicken. Over 75% of non-Dairy foodborne illnesses were attributed to Chicken, Other Seafood (such as shellfish), and Turkey, with Campylobacter illnesses most often linked to Chicken. An attribution percentage for Dairy is not included because, among other reasons, most foodborne Campylobacter outbreaks were associated with unpasteurized milk, which is not widely consumed, and we think these over-represent Dairy as a source of illness caused by Campylobacter. Removing Dairy illnesses from the calculations highlights important sources of illness from widely consumed foods, such as Chicken.

This collaborative effort to provide annual attribution estimates continues IFSAC’s work to improve foodborne illness source attribution, which can help inform efforts to prioritize food safety initiatives, interventions, and policies for reducing foodborne illnesses. These consensus estimates allow all three agencies to take a consistent approach to identifying food safety priorities to protect public health. For more information on IFSAC projects visit