Increase in Outbreaks Associated with Unpasteurized Milk, Foodborne Disease Outbreak Surveillance System, United States, 2006-2011

BACKGROUND: A federal ban prevents the interstate sale of unpasteurized milk; however, the laws regulating intrastate sales vary from state to state.  Consumption of raw milk can cause serious infections with a number of foodborne pathogens, including Escherichia coli, Salmonella, and Campylobacter. 

METHODS: We reviewed foodborne disease outbreaks reported to CDC’s Foodborne Disease Outbreak Surveillance System (FDOSS) from 2006 to 2011 where unpasteurized milk was the implicated food.   We analyzed data reported including the number of outbreaks over time, etiologic agent, number of cases, outcomes, age group, and source of unpasteurized milk.  The legal status of unpasteurized milk sales in each state was obtained from an online search of state regulations. 

RESULTS: In 2006-2011, 69 outbreaks associated with unpasteurized milk were reported from 24 states, resulting in 796 illnesses and 64 hospitalizations.  No deaths were reported. Fifty-five percent of the cases were in children ≤19 years of age. The number of outbreaks increased from 19 in the first two years of the surveillance period to 33 in the last two years.  Campylobacter was the most common etiology, causing 50 outbreaks (77%), followed by Shiga toxin- producing Escherichia coli (12 outbreaks, 18%), Salmonella (2 outbreaks, 3%), and Coxiella burnetii (1 outbreak, 1%).  Four outbreaks involved multiple etiologies.  The number of outbreaks caused by Campylobacter doubled from 13 in 2006-2007 to 26 in 2010-2011.  Among the 24 states which reported outbreaks associated with unpasteurized milk, states with legal sales of unpasteurized milk had the most outbreaks, including Pennsylvania (10 outbreaks) and Minnesota, New York, and Washington (6 outbreaks each).  Six (9%) of the 69 outbreaks were reported from states where sales were completely illegal (i.e., completely prohibited in all forms).  The source of the unpasteurized milk was reported for 55 reports.  Milk was obtained directly from a dairy farm in 34 (62%) outbreaks, licensed/commercial sellers in 14 (25%) outbreaks, and cow shares in 7 (13%) outbreaks.

CONCLUSIONS: Outbreaks associated with unpasteurized milk continue to pose a substantial public health risk. The number of outbreaks associated with unpasteurized milk, particularly those caused by Campylobacter, has increased substantially in recent years. At the same time, the number of states where unpasteurized milk sales were completely illegal decreased from 25 in 2006 to 16 in 2011. State legislatures should be aware of the risks to public health posed by unpasteurized milk as they consider legislation regarding its sale.