“…Genetic variation is generated by the accumulation of mutations during replication and their re-arrangement by genetic recombination, and genome segment reassortment in the case of segmented genomes. Mutant swarms are established within single infected cells and cell clusters (Del Portillo et al, 2011; Jung et al, 2002; McWilliam Leitch and McLauchlan, 2013; Sala et al, 1994; Sobesky et al, 2007) and in infected organisms during disease episodes, outbreaks, epidemics and pandemics [(Gire et al, 2014; Martell et al, 1992), among many other studies that have been reviewed (Domingo et al, 2012)]. Basic features of quasispecies dynamics can be studied experimentally because mutant swarms are also generated upon replication of molecular or biological viral clones in cultured cells.…”