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PB2 E627K in H5N1 Wild Bird Flu In Russia
October 31, 2005
Sequences of the PB2 gene from two isolates at Novosibirsk (A/duck/Novosibirsk/56/05(H5N1) and A/grebe/Novosibirsk/29/05(H5N1)) have been made public at GenBank. The PB2 gene sequence has been of interest because the 16 isolates from Qinghai Lake had the E627K polymorphism which has been linked to increased virulence in mice as well as a poor outcome in human or tigers infected with H5N1 carrying the polymorphism.
The E627K polymorphism had been strictly segregated by species prior to the reported isolates from Qinghai Lake. All H5N1 isolates from birds had an E at position 627, while all human isolates with a human serotype (H1, H2, or H3) has a K at that position.
Surprisingly, all 16 Qinghai Lake isolates had E627K, which has also been isolated from mouse brains. The two sequences at GenBank from Novosibirsk also had the E627K polymorphism.
Also of interest were three polymorphisms shares by the Qinghai Isolates and European swine. Surprisingly, the Novosibirsk isolates only had the third polymorphism found in swine. The first two polymorphisms were wild type. The relationship between these changes that were in all 16 Qinghai Lake isolates, and infections in humans is unknown. Third party boxun reports described human H5N1 cases at Qinghai Lake, but such human infections in Russia, Kazakhstan, and Mongolia were not reported. However, there have been reported human cases with bird flu symptoms in Hunan as well as newly confirmed cases in Vietnam, Thailand, and Indonesia, which may be related to the arrival of wild birds.
Today's announcement of H5 in wild birds in Canada is cause for concern. The crested grebe in Russia was asymptomatic and H5 is rarely detected in Canada, so the 28 infected birds in Quebec and 5 in Manitoba is cause for concern.