Commentary
H5N1 in Whooper Swans in Aomori Japan
Recombinomics Commentary 13:05
May 22, 2008
Aomori Prefecture. Towada lake Two of the swans were recovered from the H5N1 strain has been detected on Tuesday
Towadako Aomori Prefecture near the border of Akita Prefecture and the east coast of Oirase Gorge found in the estuary
The above translation describes the detection of H5N1 in two more whooper swans this week. They were in the same Towada Lake where the first positives were found a month ago (see satellite map). These swans were on the east side of the lake and therefore in the Amori Prefecture. A new outbreak in Korea was also reported this week, suggesting a new wave of birds may be migrating through the area.
The sequences of two isolates collected last month were virtually identical. There were Fujian (clade 2.3) reassortants with an HA related to clade 2.3.2. The other seven gene segments were related to clade 2.3.4. The NA sequence is most closely related to a human isolate from Guangdong province in 2006. The HA is closely related to a wild bird sequence from Hong Kong in 2007 which has been selected as the clade 2.3.2 vaccine target, but the sequence has been withheld. It is not clear of the withholding is linked to publication, or if the publication centers on the fact that the isolate is a reassortant. However, both isolates from Japan are reassortants, and the identity level of 99.7% or higher suggests the isolates in Korea are also Fujian reassortants linked to wild birds in Hong Kong..
Fujian sequences have not been reported previously in long range migratory birds like whooper swans. The detection in Japan over a one month period suggest that the level of Fujian infections is high, which is supported by the record levels reported in Korea, and the first reported H5N1 case in Primore in southeastern Russia.
The repeated detection of H5N1 in whooper swans in multiple locations over a one month time period raises additional concerns regarding an expanded geographical reach of H5N1. The current expansion in northeastern Asia involves the Fujian strain which has been more commonly reported in southern China and southeast Asia. Prior to the lab confirmation of H5 in the soldier in South Korea, the human Fujian isolates had been limited to the large clade 2.3.4 sub-clade. Since the 2007 / 2008 wild bird sequences in Hong Kong have not been released, it is not clear when the 2.3.2 / 2.3.4 reassortant formed, but its presence in long range migratory birds in locations in Japan and Russia in regions which have not previously reported H5N1 raise concerns of a significant global expansion of Fujian H5N1, which includes migration to North America.
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