[The circular life of viruses].

Circular RNAs (circRNA), as ancient as the first viruses, take an important part in the host-pathogen relationship. After the first description of dysregulated cellular circRNAs upon viral infection, numerous circRNAs of viral origin were identified and characterized. They are impacting both viral and cellular cycles and are associated with virus-induced oncogenesis, immune system regulation and cell differentiation. While the naïve reader might get swamped by discovering this new field of RNA biology, it seems that these RNA rings are actually full of surprises and wonders at both a functional and a biogenesis level.