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.

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%