Qinghai H5N1 Migration Into Germany
Recombinomics Commentary
July 1, 2007
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.
The above comments on a phylogenetic analysis of recent isolates from Bavaria and Saxony in Germany raise the possibility that H5N1 has been circulating undetected in Western Europe for the past 12 months. Almost exactly one year ago, there was a massive outbreak of H5N1 in Tyva in Siberia and in adjacent Mongolia. These sequences were closely related to 2006 sequences from Afghanistan and Azerbaijan. Recent isolates from Moscow and Krasnodar are also related to these sequences. Since the Moscow sequences are not mentioned in the phylogenetic analysis, the recent German sequences may be more closely related to the earlier sequences from Afghanistan, which are publicly available at Genbank. The Azerbaijan sequences are also public, but only available at Los Alamos. It is unclear if they were not mentioned because they are only at Los Alamos, or if the sequences in Germany are more closely related to the Tyva/Mongolia sequences.
However, the 99.5 percent identity in the HA1 sequences indicates that the Bavaria and Saxony sequences are distinct, as was seen in German sequences from 2006, as well as other public and private sequences from Europe. The relationship of the 2007 sequences to each other, as well as the earlier 2006 sequences suggest H5N1 has been circulating undetected in Western Europe for the past 12 months. The sequence relationships mimics those of wild birds in 2006. In 2006 over 700 wild bird samples were H5N1 positive. In many countries, like Germany this year, the wild bird sequences were reported in the absence of any poultry sequences in the country. Moreover, none of these countries had reported “Asian” H5N1 prior to 2006, and all isolates in 2006 and 2007 were clade 2.2 (Qinghai strain). Moreover, sequences from H5N1 in a healthy teal, isolated in December, 2005 was virtually identical to sequences in wild birds and an asymptomatic cat from Austria, indicating H5N1 was circulating in the fall of 2005 in Western Europe. No country in Western Europe reported H5N1 infections in wild birds or poultry in 2005, again suggesting a lack of sensitivity in the surveillance programs.
The presence of H5N1 in western Europe in 2007 increases pandemic concerns. In May, 2005 H5N1 was reported in long range migratory birds. As expected, this movement into this population lead to a dramatic expansion of the H5N1 geographical reach. Prior to May, 2005, no country west of China had reported “Asian” H5N1 in wild birds or poultry. After May, 2005, almost 50 countries in Europe, the Middle East, and Africa reported H5N1 infections in poultry and/or wild birds. All reported outbreaks were the Qinghai strain (Clade 2.2).
The expanded geographical reach led to the acquisitions of a number of regional markers which allowed for polymorphism tracing. This tracing established migration / acquisition routes for specific polymorphism which are acquired via recombination. As was seen for NA G743A, it was appended onto six different clade 2.2 genetic backgrounds in Moscow, Egypt, and Ghana. Because of linkages between Moscow, Azerbaijan, and Afghanistan, the acquisition of this polymorphism in 2007 isolates in Germany and Afghanistan would be of interest. However, the acquisition by the six distinct genetic backgrounds in three countries in 2007 clearly demonstrates recombination between sequences transported and transmitted by wild birds.
An understanding of H5N1 evolution, and selection of vaccine targets would be significantly advanced by the release of clade 2.2 sequences from the 2005/2006 outbreaks in Europe, as well as 2007 outbreaks in Germany, the Czech Republic, Turkey, Kuwait, Afghanistan, and Pakistan.
Moreover, serious surveillance in neighboring countries, and prompt reporting of H5N1 infections in wild birds and domestic poultry would be useful.
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