Fig. 2

SARS-CoV-2 Mutation occurrence over time divided per geographic area. Eight novel recurrent hotspots mutations (namely 1397, 2891, 14408, 17746, 17857, 18060, 23403 and 28881) and 5 hotspots already reported in literature (namely 3036, 8782, 11083, 28144 and 26143) were subdivided first into 5 period subgroups: December 2019 (n = 5), 1st–15th Jan. 2020 (n = 15), 16th–31st Jan 2020 (n = 52), 1st–15th Feb 2020 (n = 13), 16th–29th Feb 2020 (n = 55) and 1st–13th Mar 2020 (n = 80). Next, for each time group, a further subclassification per geographic area (Asia, Oceania, Europe and North America) was performed (number of genomes in each area are reported in the figure inset). The number of mutations in each area was normalized by the number of genomes analyzed for each period of time. This figure shows that mutation frequency increases over time during viral spread out of Asia. No mutations were observed in the Asian genomes analyzed in December 2019. In the time group of February 16th–29th, a defined cluster of mutations emerged in Europe; in March 1st–13th, a different cluster of mutations emerged in North America