EXCERPT

Its genetic code is roughly twice the size of the record-holding Megavirus. And it seems almost completely unlike anything else on the planet. Only 6 percent of its genes resembled the genes other organisms. [Jean-Michel Claverie of Aix-Marseille University in France] says he thinks the Pandoraviruses may come from a different origin – perhaps radically different.

SOURCE

http://www.npr.org/blogs/health/2013/07/18/203298244/worlds-biggest-virus-may-have-ancient-roots

ARTICLE

Philippe, N., et al. 2013. Pandoraviruses: amoeba viruses with genomes up to 2.5 Mb reaching that of parasitic eukaryotes. Science 341(6143):281-286.