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Millions of birds have been infected by the highly contagious disease.
"While the avian influenza outbreak does not pose a risk to humans, we are taking the matter very seriously and believe declaring a state of emergency is the best way to make all resources available," said Branstad in a press release.
Read MoreIowa reports additional 5M+ likely bird flu cases
"Even before the virus began in Iowa, our office was monitoring the outbreak in other states. We'll continue our work—as we've been doing since the first outbreak in Buena Vista County—in hopes of stopping the virus' aggressive spread throughout Iowa."
Iowa, the top egg-producing state in the United States, is the third state to declare a state of emergency because of the viral outbreak, which either has led or will lead to the extermination of up to 21 million chickens and turkeys nationwide.
Minnesota and Wisconsin declared states of emergency in April.
At the time this story was published, 21 sites in 10 counties across the state have reported cases of the disease. The counties include: Buena Vista, Cherokee, Clay, Kossuth, Madison, O'Brien, Osceola, Pocahontas, Sac and Sioux.