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H5N1 in Wild Bird in Hong Kong
January 4, 2007
Dr Thomas Sit of the Agriculture, Fisheries and Conservation Department, said tests on the bird revealed it had died of the H5N1 virus and that it could signal the start of the bird flu season in Hong
"I would suspect, as would many animal health authorities in the world, that migratory birds may be the first to carry the virus and then infect wild
birds," he said.
The above comments describe the first reported case of H5N1 in 2007. The finding was not unexpected. Each season migratory birds pass through Hong Kong at this time of the year, and H5N1 infected dead wild birds are typically found. Last year the birds were infected with the Fujian (Clade 2 sub clade 3) strain of H5N1, and similar findings would be expected, although the Qinghai strain has been reported in South Korea, so that strain may also be expanding to the south. In the recent PNAS report, only one Qinghai isolate was reported for southern China, but the limit detection was likely due to the source of the samples, which was largely limited to wet markets.
The new season will lead to new polymorphisms, as was seen in the human H5N1 isolate in Egypt. That isolate had M230I, which is adjacent to the receptor binding domain and is found in all three human serotypes (H1N1, H3N2, and influenza B). The new acquisition creates an exact match with positions 226-230 (QSGRI) in influenza B.
Recently, the largest cluster reported to date in Egypt was just 12 miles from the index case, suggesting M230I will also be present in that cluster. This would be a cause for concern because other changes in the receptor binding domain were found in Qinghai isolates from patients in Egypt (S227N), Turkey (S227N), Azerbaijan (N186K), and Iraq (N186S and Q196R). In addition V223I has been found in a bar-headed goose in Mongolia, and K222R was in a cat in Dagestan. Similarly A188E has been found in chickens in Lagos while A189E has been found in an ostrich in Nigeria. The chnages have also been found in H5N1 isolates in northern, and southern China, which link to migratory birds carrying the Qinghai strain.
Since all of these changes in or near the receptor binding domain in Qinghai isolates, which also has PB2 E627K, migration of these sequences into new regions are likely to cause new problems.