Viruses of the family Flaviviridae are important pathogens of humans and other animals and are currently classified into four genera. To better understand their diversity, evolutionary history, and genomic flexibility, we used transcriptome sequencing (RNA-seq) to search for the viruses related to the Flaviviridae in a range of potential invertebrate and vertebrate hosts. Accordingly, we recovered the full genomes of five segmented jingmenviruses and 12 distant relatives of the known Flaviviridae ("flavilike" viruses) from a range of arthropod species. Although these viruses are highly divergent, they share a similar genomic plan and common ancestry with the Flaviviridae in the NS3 and NS5 regions. Remarkably, although these viruses fill in major gaps in the phylogenetic diversity of the Flaviviridae, genomic comparisons reveal important changes in genome structure, genome size, and replication/gene regulation strategy during evolutionary history. In addition, the wide diversity of flavi-like viruses found in invertebrates, as well as their deep phylogenetic positions, suggests that they may represent the ancestral forms from which the vertebrate-infecting viruses evolved. For the vertebrate viruses, we expanded the previously mammal-only pegivirus-hepacivirus group to include a virus from the graceful catshark (Proscyllium habereri), which in turn implies that these viruses possess a larger host range than is currently known. In sum, our data show that the Flaviviridae infect a far wider range of hosts and exhibit greater diversity in genome structure than previously anticipated.
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