Abs tract: Twelve highly pathogenic avian influenza viruses (HPAIV) of H5N1 subtype were isolated from 3 species of migratory birds in Qinghai and Tibet and 2 viruses from dead magpie and wild duck in Liaoning province in 2006. Sequence
analysis showed that the HA and NA genes of these viruses shared 97.9 % to 99.9 % sequence identity with other viruses. All 14 viruses harbored a series of basic amino acids (-RRRKKR-) at the hemagglutin (HA) cleavage site similar to the majority isolates circulating during recent years, and had a 20-amino acid deletion in the neuraminidase (NA) stalk (residues 49-68), Phylogenic analysis suggested that viruses isolated from wild bird in 2006 were originated from those in 2005, and likely have evolved to a separate clade of which 4 viruses from Liaoning formed a closer clade. These results indicated that the highly pathogenic avian influenza viruses remain exist in nature.

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