Tracking food-borne disease is also complicated by the number of illnesses thought to be caused by unknown pathogens.

ECONOMIST: Food poisoning

The study analyzed food-borne disease outbreaks for 11 years from 1998 through 2008 to calculate an annual rate.

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"They actually started writing a plan for food-borne disease outbreaks, but they started a pandemic preparedness plan, " Gresham says.

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The recent news on food-borne disease has been both good and bad.

ECONOMIST: Food poisoning

There are estimated to be 81m cases a year of food-borne disease in America, causing 9, 000 deaths, from 20 or more different microbes.

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Arizona, for example, has seen a twofold increase in salmonella reports, with an uptick beginning in June, said Dr. Joli Weiss, food-borne disease epidemiologist for the state Department of Health Services.

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The Centers for Disease Control and Prevention estimates that more than 21 million cases of acute gastroenteritis in the U.S. each year are due to infection with noroviruses, and more than half of all food-borne disease outbreaks can be attributed to them.

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That represents about 23% of the 9.6 million cases of food-borne illness each year, a study released Tuesday by the Centers for Disease Control and Prevention shows.

WSJ: Vegetables Are the Main Cause of Food-Borne Illness, CDC Study Finds

There were no findings of food-borne sources of salmonella, but she couldn't comment on whether any employees tested positive for the disease at the time.

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