ST. PAUL, Minn. (AP) — The bird flu is spreading to additional poultry flocks in Minnesota, according to the state Board of Animal Health.

The latest outbreak of avian influenza has now affected 13 flocks in the state, up from seven last Friday.

The newly reported cases all are in commercial turkey flocks — two in Kandiyohi County and one each in Becker, Dodge, Le Sueur and Stearns counties, Minnesota Public Radio News reported.

Previously, the bird flu was found in commercial flocks in Kandiyohi, Lac qui Parle, Meeker, Morrison and Stearns counties, as well as backyard flocks in Mower and Stearns counties.

The affected flocks so far include more than 580,000 birds.

Birds in affected flocks are euthanized as part of efforts to keep the virus from spreading. The outbreak is s a serious threat to Minnesota’s turkey industry, with nearly 700 farms that raise about 40 million birds a year.

In 2015, 9 million birds in Minnesota were killed by the virus or euthanized to slow its spread.

The U.S. Centers for Disease Control and Prevention has said the avian influenza strain is a low risk to the public. No human cases of avian influenza have been detected in the U.S.

A U.S. Department of Agriculture team is helping Minnesota agencies respond to the current outbreak, including quarantining infected flocks, disease surveillance and coordinating logistics and finances.

By — Ryan Bowler