The codon pair usage clusters CSFV strains into their different genotypes. Parts of a codon pair context map alignment of 46 different CSFV isolates with known virulence status are shown. The virus isolates are divided into vaccine strains, moderately virulent strains, and highly virulent strains. The frequencies of codon pair usage are represented by different colours. Green indicates that codon pairs are strongly preferred. Red indicates that codon pairs are rejected. Black means that there is no significant difference in codon pair usage. The values were calculated using the ANACONDA 2.0 software.