Before the illnesses in Racine, Wis., flour tortillas from Chicago's Del Rey Tortilleria caused similar outbreaks at more than a dozen schools in two other states — in 2003, 2004, 2005 and 2006. In 2006, Del Rey recalled tens of thousands of tortillas after health officials linked them to illnesses at schools in Massachusetts and Illinois. And in a 2006 study of prior outbreaks, a panel of top scientists with the U.S. Food and Drug Administration even offered this warning: "Flour tortillas manufactured by Del Rey hold the potential to cause illness."

Not until earlier this year — almost six years after the first outbreaks in Massachusetts — did the government temporarily shut down Del Rey to make the company fix its sanitation and safetyproblems. No more outbreaks linked to Del Rey products have been reported.