Next, we examined CpG dinucleotide bias in the SaV genomes, as studies on other animal RNA viruses suggest that CpG suppression is a major factor in their genome evolution [40, 41] . Odds ratio of CpG and GpC dinucleotides (r CG and r GC ) and the CpG/GpC ratio were calculated to assess the degree of CpG suppression. Results confirm the presence of significant CpG suppression (r CG #0.78) in examined SaV genomes, with the only exception being the bat SaV genome (Table 4 ). r GC values are similar across examined SaV genomes, suggesting that the difference in CpG suppression is specific. All SaV genomes are found to have a slightly negative GC skew, and there is no major difference between the degree of GC skew in bat SaV and the other SaVs (Table 4 ). This suggests that the degree of cytosine deamination is not a major factor in the altered GC composition and CpG suppression in the bat SaV genome.