Disease outbreaks linked to pasteurized and unpasteurized dairy products in Canada and the United States: a systematic review

Objective Pasteurization kills harmful microorganisms found in milk. While consumption of unpasteurized milk and its products is discouraged due to increased risk of infections, some individuals prefer unpasteurized dairy products. Our objective was to estimate the burden of illness from outbreaks arising from consumption of unpasteurized and pasteurized dairy products in Canada and the United States. Methods We conducted a systematic review of dairy-associated outbreaks in Canada and the USA from 2007 onward. We searched MEDLINE, Embase, Cochrane Library, TRIP Database for guidelines, and North American government agency websites up to October 2020. We included outbreak reports where the pathogenic microbe was confirmed in both the patient and the dairy product through laboratory testing. Synthesis Thirty-two disease outbreaks were linked to dairy consumption. Twenty outbreaks involving unpasteurized products resulted in 449 confirmed cases of illness, 124 hospitalizations, and five deaths. Twelve outbreaks involving pasteurized products resulted in 174 confirmed cases of illness, 134 hospitalizations, 17 deaths, and seven fetal losses. Listeria accounted for 10 out of 12 outbreaks from pasteurized products from 2007 through 2020. Conclusion Public warnings about the risk of unpasteurized dairy consumption need to continue and pregnant women and immunocompromised hosts need to be made aware of foods at high risk of contamination with Listeria.

Automated summary

Both pasteurized and unpasteurized dairy products can cause disease outbreaks, but outbreaks from unpasteurized products have more cases and higher mortality rates. Listeria is the main pathogen responsible for outbreaks from pasteurized products. Continued public warnings about the risk of consuming unpasteurized dairy products are necessary, especially for pregnant women and immunocompromised individuals to be aware of Listeria contamination in high-risk foods.