SARS-CoV-2 B.1.1.7 lineage rapidly spreads and replaces R.1 lineage in Japan: Serial and stationary observation in a community

Background: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) circulates in the world and acquires mutations during evolution. To identify the new emergent variants, the surveillance of the variants of concern (VOC) and variants of interest (VOI) is ongoing. This study aimed to determine how the transition of viral lineage occurred by stationary genome analysis in Yamanashi, Japan. Methods: We performed the whole genome sequencing using SARS-CoV-2 positive samples collected from February 2020 to the end of June 2021. Viral lineage was defined by the Phylogenetic Assignment of Named Global Outbreak (PANGO) lineages. Results: We successfully obtained 325 viral genome sequences and the number of analyzed samples accounted for 15.4% of the total 2109 COVID-19 patients identified in our district. We identified 13 types of viral lineages including R.1, P.1, B.1.1.7 (Alpha) and B.1.617.2 (Delta). These virus lineages had distinct periods of expansion and decline. After the emerging of the R.1 lineage harboring E484K variant (designated VOI in Japan), the prevalent B.1.1.214 lineage were no longer identified. The R.1 lineages were temporarily prevalent afterwards, but the influx of B.1.1.7 lineage (designated VOC) led to a decline in R.1. Currently, B.1.1.7 has become dominant after mid-April 2021. Conclusion: We clearly elucidated the transition and replacement of viral lineage by the community-based analysis. The virus completely replaced by more infectious lineages, therefore, it will be necessary to continue to monitor the VOC and VOI.

Automated summary

This study in Yamanashi, Japan, identified the transition of viral lineages through genome analysis and highlighted the replacement of less infectious lineages with more dominant ones. Continued monitoring of the VOC and VOI is crucial due to the complete replacement of the virus by more infectious lineages observed in the study.