Consumers of unpasteurized milk and cheese are 840 times more likely to experience an illness compared to those who eat and drink pasteurized dairy products.
Assuming no change in consumption of unpasteurized dairy, such products contaminated with STEC, Salmonella, Listeria monocytogenes and Campylobacter were predicted to cause 761 outbreak-related illnesses and 22 hospitalizations in 2015.
Unpasteurized dairy products caused 96% of these illnesses and more than 95% of them are salmonellosis and campylobacteriosis.
More than 700 illnesses prevented per year by pasteurizing?
If all milk and cheese consumed was pasteurized, an average of 732 illnesses and 21 hospitalizations would be prevented per year in the US. Of these, 54% would be salmonellosis and 43% campylobacteriosis.
Most unpasteurized dairy–related outbreaks are caused by pathogen contamination at the farm versus post-pasteurization contamination for pasteurized products.
Researchers suggested decreasing pathogen prevalence in bulk milk tanks on raw milk farms would help to reduce illnesses.
Dr Solenne Costard, senior consultant at EpiX Analytics and lead author, said the team wanted to base estimates primarily on published outbreak surveillance data.
“This allowed us to obtain risk estimates that relied on trustworthy sources of data, and to minimize the number of assumptions in our analysis,” she said.
“This study clearly shows that consuming raw milk and cheese poses a significant food safety risk that is easily avoidable by consuming pasteurized milk products. We hope that this work helps consumers make safe choices when it comes to dairy products.”
Unpasteurized milk, drank by only 3.2% of the population and cheese, eaten by only 1.6% of the population, caused 96% of illnesses caused by contaminated dairy products.
If the percentage of unpasteurized milk consumers 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 hospitalizations by 21%.
Incidence rates of STEC, Salmonella spp. and Campylobacter spp. illnesses and hospitalizations per one billion servings were higher for unpasteurized dairy product consumers than for pasteurized dairy consumers.
Illnesses and hospitalizations caused by L. monocytogenes infections were more often attributed to pasteurized than unpasteurized cheese.
Base of estimates
Researchers used outbreak data from the National Outbreak Reporting System (NORS) to estimate the incidence rates of illnesses and hospitalizations. It is a passive reporting system possibly affected by underreporting.
They included all outbreaks during 2009-2014 in which the confirmed agents were either Campylobacter spp., Salmonella spp., STEC or L. monocytogenes and the implicated food vehicle or contaminated ingredient was milk or cheese.
Outbreaks associated with multiple products such as processed dairy items other than milk and cheese (e.g., cream, butter, yogurt, and kefir were excluded from the analysis.
Dairy consumption estimates are from the Foodborne Active Surveillance Network (FoodNet) Population Survey.
Estimates of the proportion of dairy consumers that have milk or cheese of a given pasteurization status are from the FoodNet Atlas of Exposure.
Researchers used 87 outbreaks causing 750 laboratory-confirmed illnesses and 215 hospitalizations in the analysis.
Source: Volume 23, Number 6 - June 2017
“Outbreak-Related Disease Burden Associated with Consumption of Unpasteurized Cow’s Milk and Cheese, United States, 2009 -2014”
Authors: Solenne Costard, Luis Espejo, Huybert Groenendaal, and Francisco J. Zagmutt