A study just published in Emerging Infectious Diseases compared characteristics of outbreak and sporadic, or non-outbreak, foodborne illnesses caused by four different pathogens and found evidence that most were similar regarding patients’ illness severity, gender and age. IFSAC logoThe team of scientists from the Interagency Food Safety Analytics Collaboration (IFSAC) looked at human illnesses in the U.S. from 2004-2011 caused by Salmonella, E. coli O157, Listeria monocytogenes and Campylobacter. The data were collected by the U.S. Centers for Disease Control and Prevention’s Foodborne Diseases Active Surveillance Network (FoodNet). “The analyses help assess the usefulness of outbreak data in estimating which major food categories are linked to foodborne illnesses,” according to a June 15 Constituent Update from the U.S. Food and Drug Administration. The study results provided evidence that:

  • Campylobacter, Listeria monocytogenes, and E. coli O157 outbreak illnesses are not significantly different from sporadic illnesses with respect to patients’ illness severity, gender, and age.
  • Salmonella outbreak illnesses are not significantly different from sporadic illnesses with respect to illness severity and gender. For age, the percentages of outbreak and sporadic illnesses that occur among older children and adults are also similar. However, the percentage of outbreak illnesses in the youngest age category of birth to 3-years-old was substantially lower compared with the other age groups.

FDA noted that the FoodNet data include only a portion of reported U.S. illnesses, about 15 percent of the U.S. population, and that the number of outbreaks and illnesses available for analysis was therefore limited. “For example, fewer Campylobacter illnesses were associated with outbreaks compared with the other three pathogens, which limits the strength of conclusions about Campylobacter attribution,” the agency stated. The researchers stated that their study was limited to laboratory-confirmed cases of foodborne illness. “Consequently, our conclusions are based on the assumption that persons with foodborne illness who did not seek healthcare, or did not have a specimen submitted for laboratory testing, are similar to those whose cases were included in our study,” they wrote. “Nonetheless, source attribution methods will continue to evolve and will probably include data from multiple study populations. Recently, blending of outbreak-based and case-control source attribution estimates was evaluated. “In the future, the type of analysis reported here could be used to examine more detailed case characteristics of illnesses transmitted commonly by food for similarities and differences between outbreak and sporadic cases. Currently, these types of data are not captured routinely in the U.S. surveillance systems.” Authors of the study were Eric D. Ebel, Michael S. Williams and Neal J. Golden from the U.S. Department of Agriculture; Dana Cole and Robert M. Hoekstra from CDC; Curtis C. Travis from Leidos Inc., and Karl C. Klontz from FDA.

IFSAC was created in 2011 by three federal agencies — CDC, FDA and USDA’s Food Safety and Inspection Service (FSIS) — to improve coordination of federal food safety analytic efforts and address cross-cutting priorities for food safety data collection, analysis, and use. IFSAC currently focuses on foodborne illness source attribution, which is defined as the process of estimating the most common food sources linked to specific foodborne illnesses. More information about IFSAC and its work is available here.

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