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Nigerian H5N1 Simlar to Qinghai Strain
February 8, 2006
A laboratory in Padua, Italy, identified the H5N1 strain in the Nigerian birds, OIE said in a statement. It added further tests were being carried out to determine how closely the Nigerian strain matched the H5N1 strain detected elsewhere in the world.
The Italian Health Ministry said the bird flu strain is very similar to those found in Siberia and Mongolia.
The above comments confirm that the H5N1 Qinghai strain that migrated to Siberia and Mongolia for the summer has continued along a migration path to eastern Europe, the Middle East, and central Africa. The strain became established in ling rage migratory birds in May, 2005 at Qinghai Lake. Those isolates were readily distinguished from H5N1 strains in Asia, but contained many of the same features such as the polybasic HA cleavage site, the 20 amino acid deletion in NA and the 5 amino acid deletion in NS. The Qinghai sequences were unique however and one notable change was PB2 polymorphism E627K, which had not previously been found in avian H5N1 although the polymorphisms were in all H1, H2, and H3 human isolates.
The Qinghai strain was subsequently isolated in Mongolia, Novosibirsk, Kurgan, Astrakhan, Ukraine, and Turkey and all published PB2 sequences had E627K. In Turkey, sequences from the index case also had the HA polymorphism S227N which was linked to a greater affinity for human receptors and more efficient transmission to humans. The cluster in northern Iran suggests this S227N is also being transported by wild birds and its movement into Africa may trail the H5N1 infecting birds. The suspect case in southern Iraq is the most southern human case reported thus far, but reporting of human and bird H5N1 infections has been unreliable, so the true extent of spread of H5N1 to humans remains unclear.
More sequence information of the Nigerian isolates would be useful as would more transparency in reporting H5N1 along the migratory path.