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CDC Identifies Sources of Food-Borne Illnesses Acquired in U.S.

Leafy vegetables are main culprits (Jan. 29)

For the first time, the Centers for Disease Control and Prevention (CDC) has developed a comprehensive set of estimates using data from more than a decade of food-borne disease outbreaks and previously published estimates on how many illnesses can be attributed to each food category. The new report was published online in the March 2013 issue of Emerging Infectious Diseases.

The paper builds on estimates of food-borne illness published in 2011, which showed that approximately 48 million people (1 in 6) get sick each year from food. More than 9 million of these illnesses are caused by major pathogens that the CDC tracks.

The new paper focuses on known causes of illness and uses data from nearly 4,600 outbreaks to estimate the number of illnesses that can be attributed to each of 17 food categories.

During 1998–2008, a total of 13,352 food-borne disease outbreaks, causing 271,974 illnesses, were reported in the U.S. Of those outbreaks, 4,887 (37%), causing 128,269 (47%) illnesses, had an implicated food vehicle and a single etiology. The researchers used published estimates or available data to obtain the estimated number of domestically acquired illnesses, hospitalizations, and deaths for each etiology.

The researchers attempted to attribute food categories for an estimated 9,638,301 illnesses, 57,462 hospitalizations, and 1,451 deaths caused by known agents. They did not attribute illnesses to categories for illnesses caused by astrovirus, Mycobacterium bovis, Toxoplasma gondii, and Vibrio vulnificus because no outbreaks were reported for those pathogens.

The investigators defined three categories for aquatic animals (fish, crustaceans, and mollusks); six for land animals (dairy products, eggs, beef, game, pork, and poultry), and eight for plants (grains/beans, oils/sugars [refined plant foods], fruits/nuts, fungi, and leafy, root, sprout, and vine/stalk vegetables).

The researchers applied percentages derived from outbreak-associated illnesses for each etiology to the 9.6 million estimated annual illnesses assessed and attributed approximately 4.9 million (about 51%) to plant categories; approximately 4.0 million (about 42%) to land animal categories; and approximately 600,000 (about 6%) to aquatic animal categories. Produce categories (fruits/nuts and the five vegetable categories) accounted for 46% of illnesses; meat/poultry categories (beef, game, pork, and poultry) accounted for 22%. Among the 17 categories, more illnesses were associated with leafy vegetables (2.1 million [23%]) than any other categories. After leafy vegetables, the categories linked to the most illnesses were dairy (1.3 million [14%]), fruits/nuts (1.2 million [12%]), and poultry (900,000 [10%]). Norovirus caused 57% of all illnesses.

An estimated 26,000 (46%) annual hospitalizations were attributed to land animal categories; 24,000 (41%) to plant categories; and 3,000 (6%) to aquatic animal categories. Produce categories accounted for 38% of hospitalizations and meat/poultry categories for 22%. Dairy products accounted for the most hospitalizations (16%), followed by leafy vegetables (14%), poultry (12%), and fruits/nuts (10%).

An estimated 629 (43%) deaths each year were attributed to land animal, 363 (25%) to plant, and 94 (6%) to aquatic animal categories. Meat/poultry categories accounted for 29% of deaths, and produce accounted for 23%. Among the 17 categories, poultry was responsible for the most deaths (19%), followed by dairy products (10%), vine/stalk vegetables (7%), fruits/nuts (6%), and leafy vegetables (6%). Of the 277 deaths attributed to poultry, most were attributed to Listeria monocytogenes (63%) or to Salmonella spp. (26%).

According to the researchers, the attribution of food-borne illnesses and deaths to specific food categories is useful for prioritizing public health activities; however, additional data on the specific food consumed is needed to assess per-serving risk.

Source: CDC; January 29, 2013.

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