Selection of nonstandard viral genomes during the evolution of RNA viruses: A virus survival strategy or a pesky inconvenience?

RNA viruses are some of the most successful biological entities due their ability to adapt and evolve. Despite their small genome and parasitic nature, RNA viruses have evolved many mechanisms to ensure their survival and maintenance in the host population. We propose that one of these mechanisms of survival is the generation of nonstandard viral genomes (nsVGs) that accumulate during viral replication. NsVGs are often considered to be accidental defective byproducts of the RNA virus replication, but their ubiquity and the plethora of roles they have during infection indicate that they are an integral part of the virus life cycle. Here we review the different types of nsVGs and discuss how their multiple roles during infection could be beneficial for RNA viruses to be maintained in nature. By shifting our perspectives on what makes a virus successful, we posit that nsVG generation is a conserved phenomenon that arose during RNA virus evolution as an essential component of a healthy virus community.