Evolution trace of SARS-CoV-2 from January 19 to March 12, 2020, in the United States

Evolution trace of SARS-CoV-2 from January 19 to March 12, 2020, in the United States

As a kind of human betacoronavirus, SARS‐CoV‐2 has endangered globally public health. As of January 2021, the virus had resulted in 2,209,195 deaths. By studying the evolution trend and characteristics of 265 SARS‐CoV‐2 strains in the United States from January to March, it is found that the strains can be divided into six clades, USA clade‐1, USA clade‐2, USA clade‐3, USA clade‐4, USA clade‐5, and USA clade‐6, in which US clade‐1 may be the most ancestral clade, USA clade‐2 is an interim clade of USA clade‐1 and USA clade‐3, the other three clades have similar codon usage pattern, while USA clade‐6 is the newest and most adaptable clade. Mismatch analysis and protein alignment showed that the evolution of the clades arises from some special mutations in viral proteins, which may help the strain to invade, replicate, transcribe and so on. Compared with previous research and classifications, we suggest that clade O in GISAID should not be an independent clade and Wuhan‐Hu‐1 (EPI_ISL_402125) should not be an ancestral reference sequence. Our study decoded the evolutionary dynamic of SARS‐CoV‐2 in the early stage from the United States, which give some clues to infer the current evolution trend of SARS‐CoV‐2 and study the function of viral mutational protein.

Basing on decoding the characteristics and evolution process of SARS‐CoV‐2 in the early stage of the USA, it is suggested that the clade O in GISAID should not be as an independent evolutionary clade by phylogenetic analysis or protein alignment. Secondly, Wuhan‐Hu‐1 (EPI_ISL_402125) should not be as an ancestral reference sequence and its candidate should be EPI_ISL_529213. Thirdly, many unique mutation sites in viral proteins were found to lay foundation to study the function of the mutational protein and to reveal the evolution trend of SARS‐CoV‐2 in coming days.