H7N9 - Neuraminidase
We gratefully acknowledge the authors, originating and submitting laboratories of the sequences from GISAID’s EpiFlu™ Database on which this analysis is based. A list of the sequences, their submitting labs and GISAID links is provided on this page.
The new Human H7N9 neuraminidase sequences have a partial stalk deletion between amino acid positions 67 and 73.
In N1 neuraminidases (particularly Highly Pathogenic Avian Influenza H5N1) stalk deletions are associated with adaptation to and transmission in domestic poultry (chickens and turkeys).
I think this implies that the N9 segment has been previously circulating in poultry, however there are not very many full genome asian HXN9 sequences in the database to test this hypothesis.