TABLE 2.

Amino acids that distinguish the 1918 strain from the avian clade

Amino acid position	Amino acid in indicated strain:
	1918	Human	Swine	Equine	Avian
16	D	D	G	G	G
33	I	I	I	V	V
100	I	V	Ia	R	R
136	M	M	M/I	L	L
283	P	P	L	L	L
313	Y	Y	F	F	F

^aA few strains have V at this position.