Outbreaks of E. Coli O157:H7 and Campylobacter Infections Associated with the Consumption of Commercial Raw Milk, California 2006-2012

BACKGROUND:  Outbreaks of bacterial pathogens, including Shiga-toxin producing Escherichia coli (STEC), Salmonella spp, and Campylobacter have been associated with the consumption of raw cow milk and raw dairy products. States that permit the sale of raw dairy products have a higher incidence of raw dairy-associated outbreaks than states that prohibit such sales. In California, two certified raw dairies, Dairy A and Dairy B, sell their products commercially.

METHODS: Foodborne outbreaks are reportable, and reports of foodborne outbreaks between 2006 and 2012 where commercial raw dairy products were implicated as the vehicle were reviewed. Details of the outbreak investigations, including epidemiologic analysis, laboratory studies, and onsite dairy inspections were evaluated.

RESULTS: During 2006-2012, we identified five outbreaks associated with commercial raw milk consumption, two due to STEC O157 and three due to Campylobacter. The outbreaks of STEC O157 infections were smaller in size (five and six patients) and younger in age (median six years) than the Campylobacter outbreaks. However, the illnesses were severe, with approximately 50 percent hospitalized, largely due to hemolytic uremic syndrome. The three Campylobacter outbreaks consisted of eight, eleven, and nineteen case-patients with a median age of 17 years; one patient required hospitalization. Dairy A was determined to be the source of illness for both STEC O157 outbreaks as well as two of the Campylobacter outbreaks; 100 percent of case-patients reported exposure to Dairy A raw milk products, with supporting evidence from environmental sampling and laboratory testing. Dairy B was the source of one Campylobacter outbreak, with supporting evidence from environmental sampling and laboratory testing. Both dairies conduct ongoing milk sampling for coliforms, and Dairy A routinely tests for bacterial pathogens.

CONCLUSIONS:  Five outbreaks of bacterial infections have been linked to consumption of commercial raw milk in California in recent years. Notably, all five outbreaks impacted children; the median age for patients in all five outbreaks was less than 18 years of age. Ongoing monitoring and sampling of commercial raw milk has not prevented these outbreaks. Continuing public education efforts regarding the risks of raw milk and raw milk products, especially towards those at highest risk, such as children, remain important.