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H5N1 Bird Flu Migration to Russia Confirmed
July 29, 2005
"That raises the need for undertaking quarantine measures of the widest scope," the statement said. Ministry officials could not immediately be reached for elaboration……
The outbreak in Russia's Novosibirsk region apparently started about two weeks ago when large numbers of chicken, geese, ducks and turkeys began dying. Officials say that all dead or infected birds were incinerated. But it is unclear whether that would effectively stop the virus from spreading.
The announcement of H5N1 in the Chany Lake area was not a surprise. The timing of the outbreak, location, and targeting of ducks and geese all pointed toward further spread of H5N1 linked to the Qinghai Lake outbreak in May. The May outbreak in Qinghai was followed by June outbreaks in Xinjiang. Thus, a July outbreak near Chany Lake in the Novosibirsk region merely extended the migration path. OIE reports all indicated the cause of the outbreaks were migratory birds.
The events were also telegraphed by the sequences of the isolates at Qinghai Lake. There were described in reports in Nature and Science. The Nature report speculated that the H5N1 came from Shantou in Guangdong Province. However, analysis of the sequences showed that there were many sequences from migratory birds, and the H5N1 at Qinghai Lake were recombinants with sequences from birds in Europe and Asia.
Moreover, many of the sequences could be traced to mammalian serotypes. The most dramatic change was in PB2. At position 1906, the G to A transition marked a dramatic breach of the species conservation of this position. The transition led to E627K, a change that had previously been associated with increased virulence and neurotropism. All human isolates had a A at position 1906, while all avian H5N1 isolates had a G. The only prior exception were H5N1 isolates from mammals. However, all of the isolates at Qinghai Lake had acquired the mammalian version. Similarly, the trio of polymorphisms, A346G, G347A, and G349A were mammalian and present in a 1999 H3N2 isolate from a child in Hong Kong as well as H1N1 and H1N2, and H3N2 from swine in Europe. These acquisitions pointed toward a European origin as well as a mammalian origin. A number of additional polymorphisms traced back to H5N2 isolates from Europe. These polymorphism had been previously seen in H5 isolates from Chany Lake as well as the Primorie region in Russia. However, these H5's did not have the multi-basic cleavage site, so the birds were asymptomatic and the H5N1, H5N2, and H5N3 could silently spread.
Now with the acquisition of the mammalian polymorphisms and multi-basic cleavage site, the distribution of H5N1 leaves a trail of dead birds. This trail has moved from Qinghai Lake north to summer in southern Russia, and now the birds will begin migrating to Europe, India, eastern China, and southeast Asia. In many of these areas, H5N1 has become endemic, and the new migratory sequences will generate new recombinants, which will cause new problems.