Phylogenetic tree hylogenetic analysis based on 3′-UTR nucleotide sequences. ● strains without neurovirulence, ▲ strains with neurological symptom. The phylogenetic tree was drawn using the neighbor joining method. Bootstrap values are shown as percentages derived from 1000 samplings and the scale reflects the number of nucleotide substitution per site along the branches.
Wen et al. Virology Journal 2013 10:115 doi:10.1186/1743-422X-10-115