Table 2. Amino acid differences between classical swine, Eurasian swine and the 2009 pH1N1 M1 proteins.

	M1 residue
	30	142	207	209
Classical Swine	D (153/153)	V (152/153)G (1/153)	S (148/153)G (3/153)N (2/153)	A (153/153)
Eurasian Swine	G (126/130)S (4/130)	A (130/130)	S (119/130)N (8/130)G (1/130)	T (130/130)
pH1N1(human 2009 isolates)	S (3,780/4,162)D (334/4,162)N (46/4,162)G (2/4,162)	A (3,825/4,162)S (330/4,162)V (6/4,162)Xaa (1/4,162)	N (3,830/4,162)S (329/4,162)others (3/4,162)	T (3,828/4,162)A (333/4,162)Xaa (1/4,162)
pH1N1(human 2010–2012 isolates)	S (699/721)N (16/721)others (6/721)	A (720/721)G (1/721)	N (721/721)	T (721/721)

Number of isolates containing the indicated residues/total number of isolates is indicated.