Fig. (2) Neighbor Joining phylogenetic tree inferred with Jukes & Cantor correction of Dutch influenza A(H1N1) virus neuraminidase (nt 171-901) (left figure) and haemagglutinin (nt 184-901) (right figure) sequences. The trees were rooted on the influenza A(H1N1) vaccine strain A/Solomon Islands/3/2006. The trees show evidence for more amino acid variation in the receptor binding site in the haemagglutinin of oseltamivir resistant strains (in bold font) compared to oseltamivir sensitive strains (plain font). Substitution coding: capitals for amino acids and lower case for nucleotide substitutions not leading to an amino acid change. Substitutions indicated on the left side of the trees are valid for all sequences after the indicated node.