Whole-genome sequence analysis of a novel orthobunyavirus isolated in Japan in the 1980s.

Two viruses isolated from Culicoides biting midges in Japan and preserved in a frozen state for over three decades were genetically characterized by next-generation sequencing. The viruses have a tripartite RNA genome with the typical coding strategy of orthobunyaviruses. They also share a high level of genetic similarity and are thus regarded as isolates of the same virus. Pairwise sequence comparisons and phylogenetic analysis including viruses of the Simbu serogroup demonstrated that the new viruses are members of clade A of this serogroup. In addition, a discrepancy in the phylogenetic trees indicated that a genetic reassortment had occurred in the evolution of the studied viruses. The L protein of the virus reported here showed no more than 94.6% amino acid sequence identity to that of any other Simbu serogroup virus, indicating that it should be regarded as a novel virus according to a criterion for species definition in the genus Orthobunyavirus. Therefore, this novel virus is tentatively named 'Taniyama virus' based on the location where the infected midges were collected.