TABLE 4.

Average nucleotide substitution rate in ORF2 to ORF7 of PRRSV persistent isolates

Genome region	Ratio of nonsynonymous substitutions per site/synonymous substitutions per site at dpi:
	84a	150b
Nsp1α	1.330	0/0.002c
ORF2	0.800	0/0.001c
ORF3	1.146	0.730
ORF4	1.964	0.790
ORF5	2.515	1.000
ORF6	0.090	0.002/0d
ORF7	0/0.001c	0/0.001c

^aAverages of five animals (3-84b, 22-84b, 27-84b, 31-84b, and 32-84b). 

^bAverages of two animals (3-150b and 31-150b). 

^cAll nucleotide changes were synonymous. 

^dAll nucleotide changes were nonsynomous.