Nearly a dozen commercial farms in Sonoma County, north of San Francisco, have had to kill more than a million laying hens. State health officials have urged farmers to keep their flocks indoors until June, including organic chickens that must have access to the outdoors.
Waterfowl can carry the virus without getting sick and easily spread it through their droppings to chicken and turkey farms and backyard flocks through droppings and nasal secretions. The outbreak has been a severe economic blow for farmers, workers and their customers.