LAUSR

Part of the difficulty in scientific understanding of the SARSCoV-2 epidemic is the lack of knowledge about viral evolution. Thus, this goes back to the definition of viruses that opposed those who saw only bioactive molecules (Stanley, Nobel Prize for Chemistry in 1946) and those who saw them as small living organisms, such as Burnet (Nobel Prize for Physiology or Medicine in 1969). In reality, apart from controversies regarding their definition, viruses are variable adaptive elements having mutations adapted to the setting, specializing in a given host and capable of being selected under the selection pressure of environmental parameters [1,2]. In practice, viruses are part of our ecosystem and evolve accordingly. Simplifications regarding epidemiology, therapy or vaccination are likely to be dangerous. The most known example has been that of influenza virus, for which new variants appear regularly [3]. The fight against viruses does not consist in fighting against a fixed object but against a moving target. RNA viruses are the major entities involved in emerging diseases because of their gigantic zoonotic reservoir [4] and their variability, each replication generating a hundred times more mutations than for a DNA virus or any living entity with a DNA genome [2]. Under these conditions, RNA viruses constantly accumulate mutations [1,2]. For SARS-CoV-2, this was neglected for several months and we first reported the existence of variants in early September 2020 [5], three months before the term variant was adopted in December 2020 for the Alpha variant [6]. Since 2021, the WHO has defined variants of interest and of concern [7]. We defined the variants as clades