IFSAC uses a method to estimate the percentages of foodborne illnesses attributed to certain sources using outbreak data from 1998 through the most recent year for IAFSC’s priority pathogens: Salmonella, E. coli O157, L. monocytogenes, and Campylobacter. Unlike in prior IFSAC annual reports, attribution estimates for Campylobacter are not presented in the 2020 report. Evidence suggests the sources of Campylobacter outbreaks likely differ considerably from the sources of non-outbreak illnesses caused by the pathogen. IFSAC is exploring alternative approaches for estimating the sources of Campylobacter illnesses.