Bird flu has apparently infected a second backyard flock in the Tri-Cities area of south-central Washington, according to the Washington State Department of Agriculture (WSDA).

Capital Press reports that the second flock was exposed to the highly pathogenic H5N2 virus by domestic ducks transferred from the first infected flock.

The 100 birds in the first flock — a collection of ducks, chickens and turkeys — were euthanised on 5 January.

The 500 birds in the second flock were due to be euthanised on 6 January, WSDA spokesman Hector Castro, told the newspaper.

Bird flu has not been confirmed in the second flock but birds are dying at an unusual rate, he said, adding, “All the signs are this flock was infected.”

The ducks were moved between the flocks, which are about nine miles apart, around Christmas, before bird flu was detected around New Year’s Eve in the first flock, Mr Castro said.

The flock owners know each other and exchange birds, he said.

WSDA and US Department of Agriculture officials have set up surveillance zones within about six miles of the two flocks. Officials planned to look for other signs of bird flu cases.

Mr Castro said backyard flocks are common in the area.

Officials suspect the first flock was infected by migratory waterfowl, according to Capital Press. A wild duck and captive gyrfalcon that was fed wild duck were infected by highly pathogenic avian influenza in December.

Also in December, a 100-bird backyard flock in Winston in southern Oregon on property with a pond and marsh was infected with highly pathogenic avian influenza.

Implications for US Poultry Exports

Bird flu has not been detected in US commercial poultry but the infections in backyard flocks has cost the United States its designation as a country free of highly pathogenic bird flu, according to Capital Press. Several countries have restricted US poultry imports.

Some 17 countries reacted on 5 January to the outbreak in the Washington backyard flock with new import restrictions on US poultry meat and other poultry products.

Only Sri Lanka banned all US poultry, joining several nations that imposed such bans after highly pathogenic bird flu was detected in Whatcom County in Washington, and Douglas County in Oregon. The USDA has criticised bans on all US poultry as unwarranted.

Most nations have focused their bans on Washington and Oregon. They include Nicaragua, Uruguay, Guatemala, Cuba, El Salvador, Costa Rica, Peru, Colombia, Ecuador and Belarus.

Hong Kong restricted imports from Benton County, Washington. It had previously banned imports from Douglas County, Oregon.

The Capital Press report adds that avian flu has been found in 11 commercial poultry operations and one backyard flock in British Columbia, Canada.

Highly pathogenic bird flu had never been detected before in Washington or Oregon and had not been seen in the United States for a decade.

Backyard flock owners will be compensated for euthanised birds through a USDA programme.

WSDA officials explained that the greatest risk for bird flu spreading is from migratory waterfowl coming in contact with domestic birds. Officials advised flock owners to keep their birds away from wild birds.