Phylogenetic analysis
Phylogenetic evaluation of HA and NA genes was done using Mega 7, neighbour-joining method, phylogeny test by bootstrap method and 1000 replications, Kimura 2 substitution model and partial deletion (site coverage cutoff 5%). The viruses were compared with A(H1N1)pdm09 reference viruses according to McCauley et al. (2019) (11). The identified substitutions (see FluSurver analysis) were assigned to protein domains (region of antigenic sites and receptor binding sites) according to the FluSurver database and Igarashi et al. and Yang et al. (5, 12).