Last week, researchers at the International Conference on Emerging Infectious Diseases in Atlanta reported that food borne outbreaks of infection linked to lettuce and other leafy green vegetables are on the rise, and not just because Americans are eating more salad than ever before.

Investigators from the Centers for Disease Control analyzed data from 1973 to 2006 and found that 5% of food borne disease outbreaks were linked to leafy greens. While almost 22 million pounds of frozen hamburger patties were recalled in 2007 due to contamination with the bacteria E. coli, more than half of the outbreaks associated with leafy greens were caused by a virus called Norovirus.

The investigators found that, between 1985 and 1995, U.S. consumption of leafy greens increased by 17.2%, but the proportional of food borne outbreaks due to leafy greens increased by 59.6%. And, from 1996-2005, leafy green consumption increased by 9.0% and leafy green-associated disease outbreaks increased by 38.6%.

This doesn't mean you should stop eating leafy green vegetables. It does suggest, however, that reducing contamination and increasing food safety continues to be an important public health issue.