USA Today reports that for starters, the problem has been accelerated by the American appetite for fruits and vegetables — much of it raw as the market grows for packaged fresh greens.

Americans ate 10 times more spinach in 2005 than in 1970, with much of the growth in ready-to-eat bagged spinach and baby spinach, according to the Department of Agriculture’s Economic Research Service.

Americans have increased consumption of all produce — up 25% between 1970 and 2004.

Raw produce skips what Linda Harris, an expert on food safety at the University of California-Davis, calls "the kill step." That’s cooking that knocks out any pathogens that may have hitched along.

And that’s a problem, because fruits and vegetables are more likely to carry disease than they were 30 years ago, says the Centers for Disease Control and Prevention. "In the 1970s, it was two outbreaks a year. In the 1980s, it was seven a year. And in the 1990s, it was 16 a year," says Patricia Griffin, a doctor who studies food-borne and diarrheal illnesses at the CDC. Figures for the past five years are being compiled, she says.