* Amino acids in brackets indicate less than half but more than two substitutions at the given amino acid position within a season. A single amino acid change in one position is not shown. Amino acids separated by '/' indicate equal substitutions of either amino acid at the given position. Letters in upper case above an amino acid indicate the antigenic site location of the residue. In N1 the upper case letter ' P ' stands for phylogenetically important region (PIR) and the following letters indicate the actual PIR. Based on the ratio of non-synonymous versus synonymous substitutions none of the influenza A genes were directly influenced by positive selection (dN/dS<1) (Table  3) . However, as expected the HA1 region of both H3 and H1 viruses were more influenced by evolutionary pressure (Table 3) . We applied FEL and SLAC maximum-likelihood methods to estimate individual positively selected sites in H3N2 HA and NA and added REL for smaller datasets in all genes (se methods section). The FEL method found one site in the H3 protein (n = 204), position 199 (p = 0.046) to be positively selected, while the more conservative SLAC analysis found none. No positive selected sites were predicted for the N2 genes (n = 166) and none in the internal genes (n = 15) estimated by FEL and SLAC. The REL analysis retrieved four sites in the M1 gene to be selected namely positions 208, 211, 218 and 219. No sites in HA (n = 27) and NA (n = 30) of the H1N1 viruses were directly positively selected with any of the three methods of analysis. [26] and it was anticipated that there would be some extent of herd immunity in the population against this new reassortant.