AG Secretary Bill Northey talks about the bird flu along with Governor Terry Branstad.

Agriculture Secretary Bill Northey (right) joined Governor Terry Branstad to declare a state emergency Friday as bird flu cases mounted.

The Iowa Department of Agriculture reports 4 new probable cases of the bird flu in three counties. There are 3 cases involving an undetermined number of turkeys, 2 in Buena Vista and one in Cherokee counties in northwest Iowa.

The other is in a commercial laying operation in Wright County in the north-central part of the state that has an estimated 2.8 million birds.

The Wright County case is noteworthy as county officials there took steps to declare their own state of emergency Thursday before the governor took action to declare a statewide emergency on Friday.

It is the first case in Wright County — which has more poultry than any other county — with some 15 million birds in 20 operations. The new probable cases of bird flu bring the total number of laying hens impacted to more than 18 million out of 59 to 60 million birds. All of those animals will be destroyed once tests positively determine they are infected with the avian influenza.