Origins of H5N1 on Czech Turkey Farm
Recombinomics Commentary
June 21, 2007
Laboratory confirmation and data on the isolate, as well as findings
on the possible source of this outbreak, are expected. - Mod.AS
The above ProMed commentary seems to imply that the H5N1 sequence from dead turkeys in the Czech Republic may provide data on the source of the outbreak. Although this is true after a sequence has been generated, the upcoming annopuncement will likely just confirm that the H5N1 is Clade 2.2, which is the Qinghai strain, which is the only H5N1 strain that has been detected in wild birds or poultry west of China.
The Qinghai isolates do have a number of regional markers, and an exact match may signal a source. However, the number of H5N1 out of Europe this season has been quite limited because the surveillance remains poor. H5N1 from a live healthy wild bird in Western Europe has yet to be reported, although H5N1 in dead or dying wild birds has been widespread in the region, including prior detection of H5N1 in the Czech Republic. However, these isolates were from last year.
This year, H5N1 has only been reported for Hungary and England. The close relationship suggests that the H5N1 in Hungary may have been transported to England. However, that linkage is the exception rather than the rule. Most of the H5N1 detected has been diverse and has defined a number of regional markers. Thus, the H5N1 in Moscow and Krasnodar are easily distinguished from each other and the isoaltes in Hungary and England. 2007 isolates from Egypt and Ghana also had regional markers and were easily distinguished from isolates in other regions.
Thus, the origin of the Czech H5N1 will require full sequencing. The 2006 H5N1 Czech sequence was closely related to sequences from Italy and Germany. However, sequences from Germany fell into three major groups. One was like the Czech isolates, but another had multiple polymorphisms that subsequently appeared in Egypt and western Africa, while a third group was limited to northern Germany.
However, the 2007 isolates in Egypt were significantly more genetically complex than the 2006 isolates and similar evolution would be expected in 2007 isolates from the Czech Republic.
Therefore, full sequences of Czech isolates would be useful.
Media sources
Recombinomics Presentations