WILLMAR — Four new sites have been added to the Board of Animal Health's list of confirmed cases of H5N1 highly pathogenic avian influenza, bringing the state's total to 79 sites in 28 counties.

Two new confirmations — a backyard flock of 24 birds in Clay County and a commercial flock of 4,744 turkey breeder toms in Kandiyohi County — were announced Thursday, May 19, in an update from the state Board of Animal Health. The site in Clay County is the first from that county; the Kandiyohi County site marks the first time a flock of breeder turkey toms has been affected.

Two additional sites — a backyard flock of 46 birds in Polk County and a 57,000-bird commercial turkey meat operation in Dakota County — were announced Monday, marking the first sites in both affected counties.

The Board of Animal Health tally as of Tuesday shows 3,008,799 affected birds. Infected flocks are depopulated.

The U.S. Department of Agriculture defines depopulation as "when large numbers of animals must be destroyed in response to an animal health emergency."

The two main methods are water-based foam for floor-raised birds and carbon dioxide gas for caged birds. USDA says they are the most humane and effective options available in an emergency situation involving mass numbers of birds.

The vast majority of infections in Minnesota have been in commercial meat turkey operations. Other production types with confirmed diagnoses, according to the Board of Animal Health, have been four commercial turkey breeder hen flocks, three located in Kandiyohi County and one in Stearns County; two commercial chicken operations in Morrison County — one broiler flock and one egg layer flock; and 18 backyard producers.

The board's web page devoted to avian flu response in the state — bah.state.mn.us/hpai — is updated at noon each weekday with the information that is known about infection sites. Data from previous days also may be updated by quality control staff if more accurate information is gathered later.

The first Minnesota cases of the disease — which is fatal to domestic poultry — were confirmed March 25.

A total of 28 counties in the state have been impacted so far. The other affected counties are Anoka, Becker, Benton, Big Stone, Blue Earth, Carver, Chisago, Crow Wing, Dodge, Grant, Lac qui Parle, LeSueur, Lyon, Meeker, Morrison, Mower, Otter Tail, Renville, Rice, Stearns, Swift, Todd, Waseca and Yellow Medicine.