May Newly Defined Subgenotypes Va and Vb of Newcastle Disease Virus in Poultry Be Considered Two Different Genotypes?

We read with great interest the article by Susta et al. (1), wherein the authors report genetic diversity among Newcastle disease virus (NDV) strains circulating in poultry populations along with classification of genotype V into three newly defined subgenotypes, subgenotypes Va, Vb, and Vc, based on fusion (F) gene sequence analysis. Subgenotype Va was defined by interpopulational evolutionary distances from subgenotypes Vb and Vc of 10.9% and 8.7%, respectively (1). Different subgenotypes should have average interpopulational evolutionary distances per site of between 3% (0.03) and 10% (0.1). Different genotypes should have an average interpopulational evolutionary distance per site of 10% (0.1) (2). We conclude that newly defined subgenotypes Va and Vb of NDV (1) may be considered two different genotypes. Further, subgenotype Vc may be considered an ancestral or intermediate virus for both the Va and Vb genotypes.