Foodborne Disease Outbreaks Caused By Raw Milk Increased Over 2007-2012 Period: CDC
Legalization Of Raw Milk Sales In More States ‘Would Probably’ Lead To More Illnesses
Atlanta, GA—The number of foodborne disease outbreaks caused by nonpasteurized (raw) milk increased from 30 during the 2007-2009 period to 51 during the 2010-2012 period, according to a study that will appear in the January 2015 edition of the Centers for Disease Control and Prevention’s Emerging Infectious Disease journal.
For this study, a foodborne disease outbreak was defined as the occurrence of two or more cases of a similar illness resulting from ingestion of a common food.
The study’s authors reviewed outbreaks reported during 2007-12 in which the food vehicle was nonpasteurized milk.
Outbreaks attributed to the consumption of other dairy products made from nonpasteurized milk, such as cheese, were excluded.
The authors analyzed outbreak frequency, number of illnesses, outcomes (hospitalization, death), pathogens, and age groups of patients. Data on the legal status of raw milk sales in each state were obtained from the National Association of State Departments of Agriculture (NASDA) and an online search of state regulations.
During the 2007-12 period, a total of 81 outbreaks associated with raw 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 percent) outbreaks, followed by Shiga toxin-producing E. coli (13 outbreaks, or 17 percent of the total), Salmonella enterica serotype Typhimurium (two outbreaks), and Coxiella burnetii (one outbreak). Three outbreaks were caused by multiple pathogens.
The number of outbreaks increased from 30 during 2007-09 to 51 during 2010-12.
Information about the age of patients was available for 78 outbreaks.
For 59 percent of the outbreaks, at least one patient less than five years of age was involved and 38 percent of illnesses caused by Salmonella and 28 percent of illnesses caused by Shiga toxin-producing E. coli were in children one to four years of age.
How milk was obtained was reported for 68 outbreaks. Raw milk was obtained from dairy farms (48 outbreaks), licensed or commercial milk sellers (nine outbreaks), cow- or herd-share arrangements (eight outbreaks), and other sources (three outbreaks).
Of the 81 outbreaks, 66 (81 percent) were reported from states where the sale of raw milk was legal in some form: Pennsylvania (17 outbreaks), New York and Minnesota (six outbreaks each), South Carolina, Washington, and Utah (five outbreaks each).
A total of 15 outbreaks were reported in eight states in which sales were prohibited. Among these, the sources of raw milk were reported as a dairy farm (six outbreaks), cow or herd share (four), and unknown (five outbreaks).
The average number of outbreaks associated with raw milk was four-fold higher during the six-year period covered by this study (average 13.5 outbreaks per year) than that reported in a review of outbreaks during 1993-2006 (3.3 outbreaks per year).
This increase was concurrent with a decline in the number of states in which the sale of raw milk was illegal, from 28 states in 2004 to 20 states in 2011, and with an increase in the number of states allowing cow-share programs (from five in 2004 to 10 in 2008). The decision to legalize the sale of raw milk or allow limited access through cow-share programs may facilitate consumer access to raw milk, the study stated.
The legal status of raw milk sales in one state can also lead to outbreaks in neighboring states, the study continued. In a 2011 outbreak of Campylobacter infections associated with raw 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 infection in 2012 implicated raw 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 the sale of raw milk. All patients residing outside Pennsylvania had traveled to that state to buy the milk, the study noted.
“Outbreaks associated with nonpasteurized milk continue to pose a public health challenge,” the study said. “Legalization of the sale of nonpasteurized milk in additional states would probably lead to more outbreaks and illnesses.”
This possibility is especially concerning for vulnerable populations, such as children and senior citizens, who are most susceptible to the pathogens commonly found in raw milk.