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Prevalence of major viral strains of COVID-19 in 2020 and early 2021. A. The phylogenetic tree of COVID-19 from 2019-Dec to 2021-Jan plotted by the GISAID platform. Each viral strain was colored based on the pangolin lineage. B. The geographic distribution of major viral strains between 2020-Oct and 2021-Jan. C. The evolution of COVID-19 from 2020-Jan to 2021-Jan based on the frequency of major viral strains that were sequenced chronologically.
