Table 2. Residues that are specific for H5N1-HPAIV HA1 groups G1 and G2 (Figure 1A) and mutations that significantly increase the A(0.236)/A(0.076) ratio.

	Group G1	Group G2
Group-specific residues	D43, S120, (S,L)129, I151	N43, (D,N)120, 129del, T151
Mutations that significantly increase A(0.236)/A(0.076) ratio	P74S, H110R, A127T, F143Y, K153D, S188K, S223(N,I), S234P, G272S, N275S

Residue positions correspond the H5N1 numbering.