On a recent Monday morning, workers began their week on a large poultry farm in Franklin County, Washington, home to over 800,000 chickens. By the end of the day, avian flu had been discovered among some of those chickens. By the end of the week, four workers came down with the illness, which had infected only a handful of other people in the U.S. And after two more days of testing by the Benton Franklin Health District, another 10 workers at the farm tested positive.