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Fujian H5 Frequencies In US Migratory Birds
Human infections have not been associated with either virus; however, H5 clade 2.3.4 H5N1 virus has caused human death, so caution is warranted. During preparation of this article, H5N8 was reported in wild birds and poultry along the Pacific flyway; novel H5N2 virus was detected in Idaho, Oregon, and Washington; and another novel reassortant H5N1 was detected in Washington and British Columbia (5).
The above comments are from an ahead of press EID publication “ Novel Eurasian Highly Pathogenic Influenza A H5 Viruses in Wild Birds, Washington, USA, 2014” which describes the isolation of H5N8 and H5N2 viruses designated A/gyrfalcon/Washington/41088-6/2014 and A/Northern_pintail/Washington/40964/2014, respectively (which were released at Genbank in association with the acceptance of the above paper). The H5N2 sequence was from the nine samples from wild bird carcasses at Wiser Lake in Whatcom County, Washington. The four additional H5 PCR confirmed cases (1 American Wigeon and 3 Mallards) signal a high frequency in this population. The die off (which was likely due to Aspergillus) coupled with reported H5N2 infected farms in Fraser Valley (British Columbia, Canada) led to increased surveillance and the associated high detection rate.
As noted in the second quoted paragraph, surveillance in Whatcom County also lead to the detection of H5N1, designated A/American_green-winged_teal/Washington/195750/2014, which is closely related to a recently reported infected farm in Fraser Valley. Sequences from all three H5 isolates were related to a crane from Japan, A/crane/Kagoshima/KU1/2014, which was included in the eight phylogenic trees in the above paper, which showed that all three US sequences were closely related to the crane sequence. Moreover, the H5N2 sequence from the Fraser Valley index farm, A/turkey/BC/FAV10/2014, was very closely related to the northern pintail H5N2 sequence, signaling clonal expansion, which is likely also true for the H5N1 sequences from Whatman County and Fraser Valley.
The above sequences are Fujian clade 18.104.22.168 and as noted above, this clade evolved from 2.3.4 which has caused human fatal cases. Moreover, clade 22.214.171.124 as H5N6 has recently cause human fatal cases in China, once again highlighting the importance of H5.
In poultry the H5 creates a very high pathogenicity index, even when three of the eight gene segments are from low path North American wild bird sequences, as seen in H5N2, or four wild bird segments in H5N1. The presence of Fujian H5 in H5N8, H5N2, and H5N1 has led to a CDC alert warning of symptoms in cases with contact.
Similarly, the Fujian H5 in Taiwan (H5N2 A/Goose/Taiwan/0104/2015, H5N3 A/Goose/Taiwan/01042/2015, and H5N8 A/Goose/Taiwan/0103/2015) is also most closely related to the crane from Japan, but the number of wild bird segments is higher. Two of the eight segments in H5N8 are from wild bird flu sequences in China. The number increases to four in H5N2, and only two (H5 and MP) of the eight segments in H5N3 are from the lineage that links back to South Korea, yet all three serotypes in Taiwan are HPAI because of the Fujian H5, which has the same polybasic cleavage site as seen in Fujian H5N1, which has been circulating in China since 2005.
In North America these have been three Fujian H5 serotypes reported to date, and most of the 30 wild bird positives have been identified in wild birds shot by hunters. These positive confirm that the H5 is circulating in asymptomatic wild birds and the detection rate is high. In Oregon 6 H5N2 positives were found in Morrow County (3 Wood Ducks and 3 Northern Shovelers And 3 more in Columbia County (2 Mallards and 1 North Pintails) in limited testing (all confirmed on February 2), once again signaling a frequency of infections over a wide area in the Pacific Flyway, raising concerns that the the frequency of Fujian H5 in wild birds is increasing, leading to a higher infection rate in farms as wild birds migrate north for the spring and summer.
Moreover, crossing flyways in Canada would set the stage for a wider geographic reach when birds migrate south in the fall.