Americans might have ever-increasing affection for toss-your-own salad bars, but that alone does not explain the increased number of foodborne outbreaks of illness linked to leafy green vegetables that has occurred over the past 35 years.
According to a press release issued today from the 2008 International Conference on Emerging Infectious Diseases, Michael Lynch of the CDC decided to investigate past foodborne disease outbreaks associated with leafy greens.
Using data from the CDC foodborne disease outbreak surveillance system, researchers analyzed over 10,000 foodborne disease outbreaks reported between 1973 and 2006.
According to the press release, approximately 5 percent of all foodborne outbreaks were linked to leafy greens. Most of these (60 percent) were caused by norovirus, but some were caused by salmonella (10 percent) and E. coli (9 percent).
Lynch said he wasn't surprised by this, but he was interested in how the foodborne outbreak numbers were so much smaller than the increase in leafy green consumption. Lynch is quoted: "During the 1986-1995 period U.S. leafy green consumption increased 17 percent from the previous decade. During the same period, the proportion of all foodborne disease outbreaks due to leafy greens increased 60 percent. Likewise during 1996-2005 leafy green consumption increased 9 percent and leafy green-associated outbreaks increased 39 percent."
As usual, more research is needed to determine other factors that might have led to the increase.
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