Report - Foodborne illness source attribution estimates for 2018 for Salmonella, Escherichia coli O157, Listeria monocytogenes, and Campylobacter

CDC issued a report "Foodborne illness source attribution estimates for 2018 for Salmonella, Escherichia coli O157, Listeria monocytogenes, and Campylobacter using multi-year outbreak surveillance data, United States" that uses outbreak data to identify the sources of foodborne illness. "

The report is from the Interagency Food Safety Analytics Collaboration (IFSAC), a tri-agency group created by the US CDC), FDA, 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.

They analyzed outbreaks that were confirmed or suspected to be caused by the four priority pathogens from 1998 through 2018. (Excluded outbreaks that met one or more of the following conditions: occurred in a U.S. territory; had no identified food vehicle or contaminated ingredient; were caused by more than one pathogen (including pathogens not included in this report); were caused by both E. coli O157 and another E. coli serogroup; or were caused by both Salmonella serotype Enteritidis and another Salmonella serotype.)

Quick take-aways...

• First, nothing really new was presented in this report.
• Salmonella had the largest amount of cases and there were cases in nearly every category.  Why? Salmonella is so prevalent in the environment.
• E.coli was predominately an issue in row crops (leafy greens) and beef.  Why? Ruminants carry it and it gets onto the row crops through irrigation of those crops with contaminated water.
• Listeria cases were primarily in dairy, fruit, and raw crops.  Meat items are further down the list, much of this due to how well the meat and poultry industry has focused on controlling it.
• Campylobacter - Chicken and raw milk (although numbers from raw milk were excluded).  People focus on Salmonella in raw chicken, but Campylobacter is an equal or greater concern.  Both handled through the same ways...proper handling and cooking.

Directly from that report:
Overall Key Results

• The results are based on 905 outbreaks caused or suspected to be caused by Salmonella, 255 by E. coli O157, 44 by Listeria, and 104 by Campylobacter (after 151 outbreaks due to Dairy were excluded).
• Estimated Salmonella illnesses were more evenly distributed across food categories than illnesses from Campylobacter, E. coli O157, and Listeria; most of the illnesses for the latter pathogens were attributed to one or two food categories.
• The credibility intervals overlap for the Salmonella and Listeria categories with the highest attribution percentages, indicating no statistically significant difference among them.

Salmonella Key Results

• Over 75% of illnesses were attributed to seven food categories: Chicken, Seeded Vegetables (such as tomatoes), Pork, Fruits, Other Produce, Eggs, and Turkey.
• The credibility intervals for each of the seven food categories that account for 75.6% of all illnesses overlap with some of the others

E. coli O157 Key Results 

• Over 75% of E. coli O157 illnesses were attributed to Vegetable Row Crops (such as leafy greens) and Beef. 
• Vegetable Row Crops had a significantly higher estimated attribution percentage than all other categories. • Beef had a significantly higher estimated attribution percentage than all categories other than Vegetable Row Crops. 
• No illnesses were attributed to Eggs or Oils-Sugars.

Listeria monocytogenes Key Results 

• Over 90% of illnesses were attributed to non-meat food categories. 
• Over 75% of illnesses were attributed to Dairy and Fruits. 
• The credibility intervals for the Dairy, Fruits, and Vegetable Row Crops categories were quite wide, partly due to the small total number of outbreaks (44). The credibility intervals overlapped each other, and the intervals for the Fruits and Vegetable Row Crops categories overlapped those for some food categories with much smaller estimated attribution percentages, such as Sprouts. 
• No illnesses were attributed to Other Meat/Poultry, Game, Eggs, Other Seafood, Grains-Beans, OilsSugars, Seeded Vegetables or Other Produce.

Campylobacter Key Results 

• Over half of non-Dairy Campylobacter illnesses were attributed to Chicken (58.3%). 
• The credibility interval for Chicken did not overlap with the credibility intervals for the other categories, indicating a significantly higher estimated attribution percentage for Chicken than for any other food category. • No significant differences in the estimated attribution percentages were found among most other food categories. 
• The majority (33/56, 59%) of chicken-associated Campylobacter outbreaks were attributed to chicken liver products, which are not widely consumed in the United States. All six chicken-associated Campylobacter outbreaks caused by both C. jejuni and C. coli were attributed to chicken liver products. • No illnesses were attributable to Eggs, Grains-Beans, or Sprouts.
•  An attribution percentage for Dairy is not presented partly because most foodborne Campylobacter outbreaks were associated with unpasteurized milk, which is not widely consumed in the United States. The attribution percentages before removing Dairy were Dairy 56.5%, Chicken 25.4%, Other Seafood 4.6%, Turkey 3.6%, and Other Meat/Poultry 3.0%, and were less than 2% for each of the other categories. The Chicken attribution percentage increased to 58.3% after removing Dairy.
• Note - The attribution percentages for Dairy are not presented in the figures for Campylobacter for several reasons. Most Campylobacter Dairy outbreaks included in the database were associated with unpasteurized milk, which is not widely consumed by the general population. Moreover, an analysis of 38 case-control studies of sporadic campylobacteriosis found a much smaller percentage of illnesses attributable to consumption of raw milk than chicken.

https://www.cdc.gov/foodsafety/ifsac/pdf/P19-2018-report-TriAgency-508.pdf