An additional 1.2 million chickens will be slaughtered to prevent the spread of the bird flu after the virus was confirmed on an Iowa egg farm in the second massive case this week. Earlier this week, 1 million chickens were killed on a Minnesota egg farm. Political Cartoons View All 1240 ImagesIowa remains the hardest hit state in the nation, with more than 17 million birds killed there since the outbreak began. In one case last year, 5 million chickens were slaughtered on a single Iowa egg farm. Nebraska comes next with more than 6.7 million birds killed, followed by Colorado's 6.26 million and Minnesota's 5.6 million.

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Organizations: Iowa Department of Agriculture, Land Stewardship, U.S . Department of Agriculture, Farmers Locations: Iowa, Taylor County, Minnesota, Nebraska, Minnesota , South Dakota