Disease outbreaks linked to pasteurized and unpasteurized dairy products in Canada and the United States: a systematic review.
Level 4 - case-series / case-control
Systematic review of epidemiological outbreak reports and case-series surveillance data
PubMed 35277846 · doi:10.17269/s41997-022-00614-y
What was done
A systematic review was conducted to evaluate the burden of illness from dairy-associated outbreaks in Canada and the United States from 2007 through October 2020. Researchers searched MEDLINE, Embase, Cochrane Library, TRIP Database, and North American government agency websites. Included reports were restricted to outbreaks where the pathogenic microbe was laboratory-confirmed in both the patient and the implicated dairy product.
What was found
Thirty-two disease outbreaks were identified. Twenty outbreaks involving unpasteurized products resulted in 449 confirmed illnesses, 124 hospitalizations, and 5 deaths. Twelve outbreaks involving pasteurized products resulted in 174 confirmed illnesses, 134 hospitalizations, 17 deaths, and 7 fetal losses. *Listeria* accounted for 10 out of the 12 outbreaks linked to pasteurized products.
Why it matters
Unpasteurized dairy remains a persistent cause of preventable foodborne illness, while contamination in pasteurized products—primarily from *Listeria*—presents severe risks of hospitalization, mortality, and fetal loss in vulnerable populations.
Limits
The review excluded sporadic infections and outbreaks lacking dual laboratory confirmation in both food and human samples, which likely underestimates true disease incidence. Exposure denominators were not analyzed to calculate relative risk per consumed serving.
Cited by
- supports Hospitalizations resulting from bacterial contamination of raw milk in the United States since the mid-1990s are in the hundreds.