A tick-borne segmented RNA virus contains genome segments derived from unsegmented viral ancestors

RNA viruses can contain a single (unsegmented) or multiple (segmented) genomic molecules. However, the evolutionary connection between these two fundamentally different forms of genome organization is unclear. We discovered a previously unidentified segmented RNA virus of ticks that, uniquely, contained two segments derived from an unsegmented flavivirus, as well as two highly divergent segments of unknown origin. In addition, copies of this virus were present in a nematode (dog roundworm). Collectively, these results demonstrate the remarkable diversity of viral genome structures as well as a previously unidentified evolutionary link between unsegmented and segmented viruses.