DES MOINES, Iowa (AP) — State officials say the bird flu virus has been found in a large egg-laying flock in northwest Iowa, plus four more poultry farms. Initial tests indicated the presence of the H5N2 virus on an egg-laying farm with 3.7 million chickens in Sioux County. Secretary of Agriculture Bill Northey said Monday the virus will cost producers about a sixth of Iowa’s 60 million hens.

Northey says other probable cases have been identified at two farms in O’Brien County, one in Osceola County and another in Sioux County. More than 2 million chickens combined were on those farms.

If the final test results are confirmed, all of the birds will be killed to prevent spread of the disease.