Elisabeth A. Mungai , Casey Barton Behravesh, and L. Hannah Gould
The number of US outbreaks caused by unpasteurized milk increased from 30 during 2007–2009 to 51 during 2010–2012. Most outbreaks were caused by Campylobacter spp. (77%) and by unpasteurized milk purchased from states in which unpasteurized milk sale was legal (81%). Regulations to prevent distribution of unpasteurized milk should be enforced.
Pasteurization is an effective way to improve milk safety; however, in the United States, illness related to consumption of unpasteurized milk continues to be a public health problem. The first statewide requirements that dairy products be pasteurized were enacted in Michigan in 1948 . In 1987, the US Food and Drug Administration banned the interstate sale or distribution of unpasteurized milk.
However, the laws regulating intrastate sales are set by each state. Regulations for intrastate sales of unpasteurized milk vary from complete bans to permitting sales from farms or retail outlets. Even in states in which sale of unpasteurized milk is illegal, milk can often be obtained through other means. For example, some states allow cow-share or herd-share agreements, in which buyers pay farmers a fee for the care of a cow in exchange for a percentage of the milk produced
Consumption of unpasteurized milk has been associated with serious illnesses caused by several pathogens, including Campylobacter spp., Shiga toxin–producing Escherichia coli, and Salmonella enterica serotype Typhimurium Despite the health risks associated with consuming unpasteurized milk, the demand forunpasteurized milk has increased. Recently, many state legislatures have considered relaxing restrictions on the sale of unpasteurized milk. We report that the number of outbreaks associated with unpasteurized milk increased from 2007 through 2012.
State and local health departments voluntarily report outbreaks to the Foodborne Disease Outbreak Surveillance System of the Centers for Disease Control and Prevention through a standard web-based form (http://www.cdc.gov/nors). We reviewed outbreaks reported during 2007–2012 in which the food vehicle was unpasteurized milk. Outbreaks attributed to consumption of other dairy products made with unpasteurized milk, such as cheese, were excluded. We analyzed outbreak frequency, number of illnesses, outcomes (hospitalization, death), pathogens, and age groups of patients. Data on the legal status of unpasteurized milk sales in each state were obtained from the National Association of State Departments of Agriculture and an online search of state regulations. The sources from which unpasteurized milk was obtained or purchased were categorized according to the description from the state outbreak reports, when available.
During 2007–2012, a total of 81 outbreaks associated with unpasteurized milk were reported from 26 states. These outbreaks resulted in 979 illnesses and 73 hospitalizations. No deaths were reported. The causative agent was reported for all outbreaks. Of the 78 outbreaks with a single etiologic agent, Campylobacter spp. was the most common pathogen, causing 62 (81%) outbreaks, followed by Shiga toxin–producing E. coli (13 [17%]),Salmonella enterica serotype Typhimurium (2 [3%]), and Coxiella burnetii[1%]). Three outbreaks were caused by multiple pathogens. The number of outbreaks increased from 30 during 2007–2009 to 51 during 2010–2012. During 2007–2009, outbreaks associated with unpasteurized milk accounted for ≈2% of outbreaks with an implicated food; during 2010–2012, this percentage increased to 5%. The number of outbreaks of Campylobacter spp. infection also increased, from 22 during 2007–2009 to 40 during 2010–2012
Within this 6-year period, the number of outbreaks associated with nonpasteurized milk increased. The number of outbreaks caused by Campylobacter spp. nearly doubled. The average number of outbreaks associated with unpasteurized milk was 4-fold higher during this 6-year period (average 13.5 outbreaks/year) than that reported in a review of outbreaks during 1993–2006 (3.3 outbreaks/year) This increase was concurrent with a decline in the number of states in which the sale of unpasteurized milk was illegal, from 28 in 2004 to 20 in 2011 and with an increase in the number of states allowing cow-share programs (from 5 in 2004 to 10 in 2008) The decision to legalize the sale of unpasteurized milk or allow limited access through cow-share programs may facilitate consumer access to unpasteurized milk The higher number of outbreaks in states in which the sale of unpasteurized milk is legal has been reported elsewhere
The legal status of unpasteurized milk sales in 1 state can also lead to outbreaks in neighboring states. In a 2011 outbreak of Campylobacter spp. infections associated with unpasteurized milk in North Carolina, where sales of this product were prohibited, milk was purchased from a buying club in South Carolina, where sales were legal. Another outbreak of Campylobacter spp. infection in 2012 implicated unpasteurized milk from a farm in Pennsylvania, where sales are legal; cases from this outbreak were reported from Maryland, West Virginia, and New Jersey, all of which prohibit sale of raw milk All patients residing outside Pennsylvania had traveled to Pennsylvania to purchase the milk
Outbreaks associated with unpasteurized milk continue to pose a public health challenge. Legalization of the sale of unpasteurized milk in additional states would probably lead to more outbreaks and illnesses. This possibility is especially concerning for vulnerable populations, who are most susceptible to the pathogens commonly found in unpasteurized milk (e.g., children, senior citizens, and persons with immune-compromising conditions). Public health officials should continue to educate legislators and consumers about the dangers associated with consuming unpasteurized milk.
Ms. Mungai is a surveillance epidemiologist at the Atlanta Research and Education Foundation and at the Centers for Disease Control and Prevention. Her interests include infectious disease epidemiology and food safety.