According to the species demarcation criteria for the genus Enterovirus defined by the International Committee on Taxonomy of Viruses, members of a species in the genus Enterovirus should share high aa identity (aa >70% in the polyprotein, aa >60% in P1 and >80% aa identity in 2C + 3CD) and compatibility in processing, replication and encapsidation . In addition, EV-E and F can be distinguished from other EVs because of their unique secondary RNA structures in the 5′UTR region (domains I* and I**) . Our genome analysis revealed that BEV-AN12 shared aa sequences and protease cleavage site positions with EV-Fs. In addition, BEV-AN12 contained domains I* and II* in the 5′UTR similarly to other BEVs. Therefore, BEV-AN12 is closely related to EV-Fs. However, pairwise identity analysis revealed that aa sequences in the VP1 region of the BEV-AN12 genome had significantly low identities to other BEVs strains (VP1 aa identity ≤58.6%). Furthermore, BEV-AN12 did not cluster with any other EV-E and EV-F in the VP1 phylogenetic tree, although its P2 and P3 regions were closely related to EV-F. The percentage of aa identity of VP1 is commonly utilized for species and sero-/genotype definition (range from 50 to 55% for heterologous species, 70 to 85 % for heterologous sero-/genotypes/homologous species, and greater than 90 % for homologous sero-/genotypes) . According to the classification definition, our results indicate that BEV-AN12 is taxonomically distant from previously reported BEVs. Therefore, we named this strain as “Enterovirus K”, which is a novel species within the genus Enterovirus. Other Japanese BEVs were classified as typical BEVs (BEV-IS1: EV-E2, BEV-IS2 and BEV-Ho12: EV-F4).