. 2010 Apr 21;84(13):6497–6504. doi: 10.1128/JVI.01603-09

TABLE 2.

Selection pressures acting on each lineage of chikungunya virus

Data set	Mean dN/dS (95% CI)			I/E^a	No. of negatively selected codons^b	Positively selected codon position^b
Data set	Overall	Internal	External	I/E^a	No. of negatively selected codons^b	Positively selected codon position^b
Asian21	0.125 (0.108-0.142)	0.095 (0.073-0.118)	0.152 (0.125-0.179)	0.63	70	NA
WAf11	0.066 (0.051-0.082)	0.040 (0.016-0.063)	0.075 (0.056-0.095)	0.53	64	NA
ECSA9	0.088 (0.060-0.115)	0.058 (0.049-0.068)	0.103 (0.080-0.126)	0.57	96	NA
Epidemic39	0.285 (0.232-0.338)	0.278 (0.056-0.497)	0.286 (0.300-0.343)	0.97	16	C-23; C-27; E1-226

I/E/, ration of internal to external values.

Significant at α = 0.05.