'Satellite' viruses must be in proximity to their 'helper' virus to replicate, but this research reports the first documented case of a satellite virus attaching itself to its helper virus. Out of 50 observed helpers, 40 had a satellite bound. Bioinformatic analysis of the satellite and helper viruses' genomes provides clues as to why the satellite may have evolved to attach to the helper, and suggests this pair may have been co-evolving for about 100 million years.
