Table 5. Amino acids at variable sites of the HA gene segment of A/H3N2 influenza viruses from the ‘N-lineage’, clade a, clade b, and singleton isolates s1, s2, s3, and s4 (Figure 6), with differing amino acids in bold.

HA site	N-lineage	s1	s2	s3	s4	Clade a	Clade b
6	N	N	N	N	N	N	I
45 (C)	S	S	S	S	N	S	S
48 (C)	T	T	T	T	I	T	T
50 (C)	G	G	E	G	G	E	G
53 (C)	D	D	D	D	N	D	D
112	V	V	V	V	I	V	V
140 (A)	K	K	K	K	K	I	K
142 (A*)	R	G	R	R	R	R	G
144 (A)	N	D	N	N	N	N	N
157 (B)	L	L	L	L	L	L	S
173 (D)	K	K	K	K	E	K	E
193 (B*)	F	F	F	F	S	F	F
199	S	S	S	S	P	S	S
225	N	N	N	N	D	N	N
275 (C*)	G	G	G	G	D	G	G
375	N	N	D	N	D	D	D
450	R	R	R	R	R	K	K

Antigenic sites are specified A–E (listed in parentheses) and sites that have been identified as undergoing positive selection denoted by an asterisk (^*) [37].