Further Analysis for Surveillance-Based Associations in Foodborne Disease: Leafy Greens and Raw Milk

Background Transdisciplinary collaborations with risk analysis practitioners may enhance epidemiologic investigations and expand public health protections in light of federal and state laws and policies. Methods Previous analysis of US outbreak data for a 16-year period (2005–2020) reported in Microsoft Access ® data tables was extended for deeper analysis of foodborne public health burdens associated with leafy greens and fluid milk, foods that triggered concerns in Hazard Identification. Surveillance-based associations were examined using graphical representation with confidence intervals estimated using Locally Weighted Scatterplot Smoothing, as well as Kendall’s tau, the Mann-Kendall test for trends, and Sen’s slope testing. For the severity of raw milk outbreaks, confidence intervals were estimated for disease severity (hospitalizations per outbreak). Results No statistically detectable increasing trend in morbidity and mortality was identified for leafy greens and raw and pasteurized fluid milks in this period; however, these are unadjusted surveillance comparisons and should not be interpreted as causal or as exposure-standardized risk estimates. In the NORS outbreak records analyzed, unpasteurized milk was associated with higher observed counts of outbreaks and hospitalizations than pasteurized milk. Overall, for raw milk at the state level, the numbers and rates of outbreaks, illnesses, and hospitalizations were heterogeneous, and the average hospitalizations per outbreak category had wide confidence intervals. Any apparent associations between state-level characteristics and reported disease burdens should be interpreted cautiously, as the descriptive patterns may reflect differences in consumption, reporting intensity, surveillance practices, and other unmeasured factors. Conclusion Refocusing on understanding the factors suggesting lower public health potential for leafy green and raw dairy farm systems may reduce burdens of communicable disease, and perhaps non-communicable disease. Future collaborative studies, including epidemiologists and risk analysts, are needed to increase transparency regarding surveillance-based associations and to promote broader deliberations that support human dietary health and wellness.