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Qinghai H5N1 Reservoir in Wild Birds in Germany
June 24, 2007
The southern German city of Nuremberg said on Sunday that the bird flu virus had been discovered in the bodies of eight dead birds found in the state of Bavaria, Germany's first confirmed cases this year.
The corpses of two more birds are being analysed to see if they also contained the H5N1 avian flu virus, a city spokeswoman said.
"The city of Nuremberg and the Veterinary Office for the region of Fuerth have established a quarantine zone in the affected areas and will continue observation activity around Nuremberg," the city said in a statement.
The above comments describe an increasing number of wild birds in Germany testing positive for H5N1. Confirmatory tests later today will conclusively show that the H5N1 in the wild birds is Qinghai H5N1 (Clade 2.2).
In February, 2006, H5N1 was detected throughout western Europe in wild birds (over 700 birds were positive). Germany had the largest number of positives, most of which were in northern Germany. However additional sequences have since become public, including those from Bavaria. The sequences of the isolates form three distinct groups.
The recommendations in the Options for the Control of Influenza VI recommend using a common numbering system to describe various H5N1 sub-clades. The Qinghai strain (all H5N1 isolates west of China) is Clade 2.2. Assigning a “2” to the sequences in Germany would allow for further sub-dividing of the sub-clades described there. Assigning numbers based on publication date, Clade 126.96.36.199 would be the isolates initially described for northern Germany. In addition to the cat and goose isolate from Germany, this sub-clade would include the buzzard isolate from Denmark, as well as the more recent sequence from the stone martin.
The more geographically dispersed sub-clade would be 188.8.131.52. This group would include isolates from the Czech Republic, Italy, Slovakia, and Ukraine. It is at the top of the tree presented last year by Ian Brown from Weybridge. Several of the polymorphisms in this group are also in the vast majority of the isolates from Egypt (sub-clade 2.2.1).
The third group, sub-clade 184.108.40.206 is also large. It is in the larger tree highlighting isolates that have NA G743A. This polymorphism concurrently appeared in 2007 isolates from Moscow, Egypt, and Ghana. A eagle owl isolate from 220.127.116.11 also has HA M230I, which was acquired this season by multiple isolates in the Nile Delta, including the Gharbiya cluster.
Thus, the isolates in southern Germany are linked to a large number of Clade 2.2 isolates in western Europe and Africa. The detection of these sequences in 8-10 wild birds representing at least species in the summer is cause for concern.
Once again, the H5N1 was detected in dead wild birds. There are no reports of H5N1 in live wild birds in western Europe, although such isolates have been sequenced in Russia and Egypt. The 2005 isolates in Russia and Egypt signal the migration of H5N1 into Western Europe in 2005 (the Egyptian isolate is most closely related to isolates from Austria), and raise serious concerns about surveillance.
Although many isolates were collected in early 2006, the failure to detect H5N1 in 2007 suggests that H5N1 has been expanding and evolving undetected in western Europe. This spread has now spilled over into a turkey farm in the Czech Republic, but the lack of detection in western Europe form over one year remains a major cause for concern.