Purpose: We have attempted to compute an accurate and easily interpretable estimate of risk of foodborne illness associated with raw dairy consumption in the state of California using publicly available data. The intended measurement of risk is number of cases per unit of food product sold per year in the state of California. The methods are intended to be replicable by any concerned citizen for any food product of interest.
Methods: Data on incidences of foodborne illness in the state of California were obtained from the Center for Disease Control’s (CDC) Foodborne Outbreak Online Database (FOOD). Only searchable years were utilized (1998-2009). Dairy exposure was taken from Headrick et al. (1997) – a report on raw dairy consumption in California obtained from the 1994 California Behavioral Risk Factor Surveillance System Survey. The California Department of Food and Agriculture reported to Headrick et al. that sales of fluid raw dairy for the year 1994 equaled 1.5 million gallons or 0.2% of all fluid milk sales in the state. We assumed consistent annual sales for the 12 year period under study.
Results: There were 2,252 illnesses associated with pasteurized dairy products in the defined study period, and 186 illnesses associated with upasteurized dairy (49 when excluding cases associated with queso fresco). Assuming consistent annual fluid milk sales in the state of California of 1.5 million gallons of unpasteurized milk per year and 748.5 million gallons of pasteurized milk per year, the 12-year incidence of foodborne illness associated with pasteurized dairy was 0.25 cases per million gallons of fluid milk sold (90% CI: 0.24, 0.26), and for unpasteurized dairy it was 10.33 (90% CI: 9.09, 11.58) cases per million gallons of milk sold. When excluding cases associated with queso fresco, the 12-year incidence was 2.72 (90% CI: 2.08, 3.36) cases per million gallons of milk sold. Relative risks when including and excluding queso fresco associated cases are 41.21 (90% CI: 37.54, 44.64) and 10.86 (90% CI: 8.60, 12.96), respectively.
Significance: The choice to consume raw dairy in the state of California comes with a demonstrable excess risk of foodborne illness. Even when discounting all cases associated with queso fresco from the numerator, the relative risk of consuming raw dairy rather than pasteurized dairy in the state of California is approximately 10.