EU643638   Mutant Influenza A virus (A/duck/Czechslovakia/56(H4N6) x A/USSR/90/77(H1N1)) neuraminidase (NA) mRNA, complete cds.   [Influenza A virus (A/duck/Czechslovakia/56(H4N6) x A/USSR/90/77(H1N1)) | 524020.3]