"Avian Flu Outbreak Takes Poultry Producers Into Uncharted Territory"

"An avian flu outbreak is sweeping across the Midwest at a frightening pace, ravaging chicken and turkey farms and leaving officials stumped about the virus's seemingly unstoppable spread.

Now reaching to 15 states, the outbreak has been detected at 174 farms, according to the U.S. Department of Agriculture. Because there's no vaccine, infected and even healthy birds must be killed to try to stop the virus, forcing the killing of 38.9 million birds and counting, the USDA says.

The particular strain of avian flu, highly pathogenic H5N2, was first confirmed in a backyard flock in Washington state. While chickens and turkeys are highly susceptible to it, it is considered a low risk for transmission to humans, according to the Centers for Disease Control and Prevention."

Peggy Lowe and Sarah Boden report for NPR's Morning Edition May 21, 2015.