H5N1 In Germany Similar to 2006 Tyva and Mongolia Isolates
Recombinomics Commentary
July 1, 2007
Further to the reoccurrence of highly pathogenic avian influenza virus
subtype H5N1 in wild birds, Germany sequence data of the hemagglutinin genes of 2 isolates obtained from infected mute swans found at Nuremberg, Bavaria, and Frohburg, Saxonia have now been generated at the Friedrich-Loeffler Institut, Isle of Riems.
Preliminary comparisons and database searches demonstrated that these 2 sequences are closely related (at least 99.5 per cent identity) but
distinguishable from each other. Other closely related sequences which are publicly available originate from H5N1 isolates made in 2006 from grebes (_Podiceps spec._) in southern Siberia and from a whooper swan (_Cygnus cygnus_) and a common goldeneye (_Bucephala clangula_) in Mongolia. In a phylogenetic analysis, these viruses form a separate cluster with H5N1 viruses isolated from chickens in Afghanistan. In addition, viruses from the Russian Krasnodar region and a virus detected in 2006 in a mute swan in Italy are associated with this cluster.
In a joint analysis performed with the Community Reference Laboratory at
VLA, Weybridge, the H5N1 virus from the outbreak in a turkey holding in the Czech Republic appears to be equidistant yet closely related (99.2 per cent identity) to those from Nuremberg and Frohburg.
Intensified monitoring among wild birds and molecular analysis of further
virus isolates should shed more light on the possible routes of
introduction and spread of these viruses in Central Europe.
The above comments leave little doubt that the wild bird deaths in Bavaria and Saxony in Germany, as well as the turkey and chicken deaths in the Czech Republic, are linked to migratory birds. Each set of sequences is distinct, as expected for introductions via migratory birds. Moreover, the similarities between the German isolates and Tyva are of interest.
Almost exactly one year ago, there were massive wild bird die offs in Tyva and Mongolia,on a par with the outbreak at Qinghai Lake in May, 2005. Although western Europe denied H5N1 infections this year. prior to the recent outbreaks, the similarity with the 2006 Tyva / Mongolia isolates suggest birds that survived the outbreak brought the H5N1 to western Europe, where H5N1 circulated for a year, undetected.
Increased surveillance is clearly indicated for all countries in Western Europe. The prevalence and sequences of H5N1 play an important role in monitoring infections and evaluating H5N1 evolution.
The analysis of H5N1 evolution has been hampered by the continued hoarding of sequences. There were over 700 European H5N1 wild bird positives in the 2005/2006 season, and the vast majority of the sequences have not been made public. Approximately 80 of these sequences were used to create an HA phylogenetic tree, which was released over a year ago at the FAO sponsored meeting in Italy.
The time for the release of these sequences has passed.
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