Migratory waterfowl are spreading bird flu in Washington state, according to the Washington State Department of Agriculture.

Bird flu was confirmed Wednesday in a commercial poultry farm in Clackamas County and a small backyard flock in Lewis County, Washington.

Migratory waterfowl are spreading the virus, according to the Washington State Department of Agriculture. “Every backyard flock is at risk right now,” State Veterinarian Amber Itle said in a statement.

The virus was previously detected at a commercial poultry farm Oct. 15 in Franklin County, Washington., and a 60-bird backyard flock Oct. 17 in Kitsap County, Washington. The outbreak at the commercial operation affected 839,700 chickens.

The federal Centers for Disease Control and Prevention confirmed two workers at the farm contracted avian influenza, the Washington State Department of Health said in a press release Thursday.

Two other workers tested positive. Tests to confirm the preliminary diagnosis are pending, according to the department.

The current outbreak of avian influenza in the U.S. began in February 2022. The virus has been detected in 48 states, infecting 512 commercial farms and 670 backyard flocks, claiming 104.26 million domestic birds.

Bird flu at commercial farm in Clackamas County caused about 150,000 birds to be euthanized, according to the Oregon Department of Agriculture. It was first case of bird flu in Oregon since March.

Washington is the only state with three outbreaks in the past 30 days, according to U.S. Department of Agriculture. Idaho has had two outbreaks, both in backyard flocks.

Single cases have been found in commercial poultry farms in California and Utah. The Utah outbreak affected 1.8 million birds, according to USDA.

Bird flu has been found in 48 flocks in Washington state since 2022. The virus has been detected in 18 of the state’s 39 counties.

Bird flu has infected dairy cattle in 14 states, including Idaho and California.

The Washington State Department of Agriculture asked birds owners to report unusual illnesses or mortalities by calling 1-800-606-3056.