G743A Acquistion in Krasnodar
Recombinomics Commentary
October 5, 2007
Sequences from the recent outbreak in Krasnodar have been released. The isolate, A/chicken/Krasnodar/300/07(H5N1) was collected September 5, 2007. It had the Tva/Mongolia/Afghanistan genetic backbone, which matches the description of the H5N1 detected in wild birds in Germany over the summer.
Analysis of the NA sequence identifies G743A, which is the acquisition described previously for isolates in Moscow, Egypt, and Ghana. Although G743A was a regional marker for a subset of isolates in Germany in 2006, it was not previously reported in the above locations. In early 2007, it appeared concurrently in each of the above locations, and was appended onto the diverse genetic backgrounds.
The latest sequence puts G743A on yet another genetic background, and it is likely that it is also on the Afghanistan sequences from 2007. The concurrent acquisition of the same polymorphism onto diverse genetic backgrounds is not easily explained by “random mutations”.
This is similar to HA M230I, which was recently noted in swine H5N1 from Indonesia. Like the NA polymorphisms described above, M230I moved from one genetic background to another. In H5N1 it was initially seen in clade 1 in Vietnam in 2005. It was first reported in clade 2.2 in an eagle owl in Germany in early 2006. That report was followed by M230I in patients and poultry in Egypt in late 2006 / early 2007. The recent sequences from Indonesia indicate M230I was also appended onto clade 2.1 in poultry and swine in late 2006 / early 2007.
These acquisitions are most easily explained by recombination between H5N1 transported and transmitted by migratory birds.
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