The growing popularity of unpasteurized milk in the United States raises public health concerns. A study published in Emerging Infectious Diseases estimates that unpasteurized milk, consumed by only 3.2% of the population, and cheese, consumed by only 1.6% of the population, caused 96% of all the illnesses from contaminated dairy products during the study period. Therefore, unpasteurized dairy products caused 840 times more illnesses and 45 times more hospitalizations than pasteurized products. The researchers examined outbreak-related illnesses and hospitalizations caused by the consumption of cow’s milk and cheese contaminated with Shiga toxin-producing Escherichia coli, Salmonella spp., Listeria monocytogenes, and Campylobacter spp. using a model relying on publicly available outbreak data. They also assessed how hypothetical increases in unpasteurized dairy consumption would affect this outbreak-related disease burden.
The researchers used outbreak data from the National Outbreak Reporting System (NORS) to estimate the incidence rates of illnesses and hospitalizations. NORS is a web-based platform that stores data on all foodborne disease outbreaks reported by local, state, and territorial health departments in the United States that have occurred since 2009. They included all outbreaks that occurred during 2009–2014 in which the confirmed etiologic agents were any of the four pathogens of interest. They found that in the United States, outbreaks associated with dairy consumption cause, on average, 760 illnesses/year and 22 hospitalizations/year, mostly from Salmonella spp. and Campylobacter spp.
If the percentage of unpasteurized milk consumers in the United States were to increase to 3.8% and unpasteurized cheese consumers to 1.9% (i.e., an increase of 20%), the number of illnesses per year would increase by an average of 19% and the number of hospitalizations by 21%. If the percentages of unpasteurized milk and cheese consumers were to double, the number of illnesses would increase by an average of 96%, and the number of hospitalizations would increase by 104%, resulting in an additional 733 illnesses/year and 22 hospitalizations/year, which corresponds to a total of 1,493 illnesses/year, most caused by Salmonella spp. and Campylobacter spp.