Proposals on Virus Taxonomy Using the Examples from the Families of Phenuiviridae, Nairoviridae, and Peribunyavidae

In recent years, the taxonomy of the families of Phenuiviridae, Nairoviridae, and Peribunyavidae in Bunyavirales was updated frequently, because many novel viruses in these families have been identified and the species demarcation criteria of these families have been changed. As per these criteria and sequence analysis, we found that the taxonomy of 19 species in these families should be revised. We presented six proposals for optimizing virus species taxonomy using the examples from these families. First, the species demarcation criteria for the same family (e.g., Peribunyavidae) should be unified. Second, the methods and parameters for the taxonomic calculation in the same order (e.g., Bunyavirales) should be unified. Third, virus species taxonomy should be based on phylogenetic relationships, rather than a cutoff value of sequence identities that is a self-contradictory demarcation criterion, although sequence identities aid virus taxonomy greatly. Fourth, virus species taxonomy should be based on the phylogenetic relationship of a key viral gene (e.g., the RdRp gene of Bunyavirales), which is important for the taxonomy of virus recombinants or reassortants. Fifth, a virus can be demarcated without a species before its biomedical significance has been revealed. Sixth, names of all viruses and virus species should be constituted exclusively with common characters (English letters and Arab numbers), to minimize difficulty in spelling and communication. These proposals are rational, flexible, and can accommodate all known viruses. They can also bridge the taxonomy history and the future demands due to their flexibility.