What SARS-CoV-2 Variants Have Taught Us: Evolutionary Challenges of RNA Viruses

RNA viruses have a rapid pace of evolutionary change. Mutations in RNA viral genomes occur at a pace that greatly exceeds that observed in other organisms and determine much of their evolutionary "behavior". For instance, RNA viruses have a great ability to cross species barriers and, hence, emerging new human and animal viruses. Indeed, emerging RNA viruses are currently the biggest health threat to humankind to emerge in a very long time. Thus, it is crucial at this time to shed some light on how the evolutionary behavior of RNA viruses shapes their epidemiolocal, fitness, and pathological features. This will contribute toward a better understanding of how to deal with these threats.