Editor's note: This story was updated on Jan 22 with new information from the APHIS.

Highly pathogenic avian influenza (HPAI) H5N1 has been detected for the first time in a US bird, in Washington state, according to a report filed by John Clifford, DVM, deputy administrator with the Animal and Plant Health Inspection Service (APHIS) of the US Department of Agriculture (USDA).

The report, posted yesterday by the World Organization for Animal Health (OIE), details a novel H5N1 virus found in a wild green-winged teal in Whatcom County that resulted from reassortment between a Eurasian (EA)-type H5N8 virus and North American avian influenza strains.

The virus was detected in a hunter-killed bird as part of increased avian flu surveillance in wild birds, according to the report. Whole-genome sequencing placed it in EA H5 clade 2.3.4.4.

Its PB2, H5, NP, and MP components are more than 99% identical to the HPAI H5N8 strain found in a wild gyrfalcon in the same county in December. It also contains PB1 genes that are 98% identical to those in a HPAI H5N2 found in a northern pintail duck, also in Whatcom County in December, as well as PA, N1, and NS components from a North American low-pathogenic wild bird lineage.

"Such findings are not unexpected as the EA-H5N8 virus continues to circulate," the report states. It concludes that the new H5N1 reassortant virus "has NOT been found in commercial poultry anywhere in the United States."

Information on the USDA Web site says that HPAI H5N1 has not been previously detected in the United States. The OIE report lists 2004 as the date of a previous occurrence of the disease, but that refers to the detection of HPAI H5N2 in Texas that year, according to a staffer in Clifford's office.

H5N2, H5N8 in Idaho

In related news, the Idaho State Department of Agriculture (ISDA) said in a news release yesterday that HPAI H5N2 has been detected in a backyard poultry flock in that state, as well as in domestic falcons. In addition, HPAI H5N8 has been detected in wild birds in the state, the agency said.

The outbreak in the backyard flock was first reported by the media on Jan 19. The detections of both strains were the result of increased surveillance, the ISDA said.

The three affected falcons and the unspecified number of poultry are both in Canyon County in southwestern Idaho, and the H5N8-positive ducks were sampled in Gooding County south central Idaho.

"Both the H5N8 and H5N2 strains of HPAI confirmed in Idaho have previously been identified in incidents in backyard domestic poultry and wild fowl in other northwestern states. It is critical that backyard flock owners and poultry producers take every opportunity to prevent contact between domestic birds and the wild waterfowl that carry the avian influenza virus," Bill Barton, DVM, ISDA state veterinarian, said in the release.

See also:

Jan 20 OIE report

Jan 20 IDSA news release

Jan 20 USDA update on recent H5N2 and H5N8 detections

CIDRAP overview on avian flu in birds