Table 2.

Catalogue of subtype-specific characteristic sites for human-to-human transmission of influenza A identified for the PB2 protein. The upper table shows characteristic sites exhibited only by H1N1 human viruses, while the lower table lists characteristic sites common to H2N2, H1N2 and H3N2. For each site, we show the same values as in Table 1, except that the human variants are subtype-specific.

Position	Char. Variants		1st Human isolate	Conservation		X-presence of A2A
	A2A	H1N1		A2A	H1N1
114	V	I	1918	100.00%	98.57%	1.43%
491	T	A	1933	98.94%	97.48%	2.52%
Position	Char. Variants		1st Human isolate	Conservation		X-presence of A2A
	A2A	HxN2		A2A	HxN2
67	I	V	1964	99.68%	97.01%	2.99%
82	N	S	1957	94.27%	97.15%	0.95%
120	E	D	1970	99.52%	96.20%	3.73%
382	I	V	1961	96.77%	98.53%	1.47%
453	PS	H	1940	98.29%	99.49%	0.29%
526	K	R	1972	99.65%	95.66%	4.34%
676	TA	I	1965	96.21%	91.47%	4.93%
682	G	S	1972	100.00%	94.56%	4.19%
684	A	S	1957	96.90%	99.63%	0.22%