Phylogeny and evolution of SARS-CoV-2 during Delta and Omicron variant waves in India

A comprehensive profile of SARS-CoV-2 variants spreading during the COVID-19 pandemic: a genomic characterization study from Chhattisgarh State, India

SARS-CoV-2 has expressively changed its sequences during the COVID-19 pandemic situation by encompassing persistent evolutionary mutational changes resulting in the emergence of many clades and lineages. Evolution of these SARS-CoV-2 variants have significantly imparted fitness advantage to the virus, enhanced its transmissibility and severity of the disease. These new variants are a potential threat to the vaccine efficacy as well. It is therefore pertinent to monitor the evolution of these variants and their epidemiological and clinical impact, in a geographic setting. This study has thus looked into the geographic distribution and genetic diversity of SARS-CoV-2 variants and the evolutionary circulation of different clades in Chhattisgarh (CG) state from March 2020 to July 2023. A total of 3018 sequences were retrieved from the GISAID database, in which 558 were submitted by us. The demographic data revealed male preponderance of 56.45% versus 43.54% females, with the overall mean age of 36.5 years. SARS-CoV-2 sequences represented many variants viz., Delta (55%), Omicron (22%) and others (15%) with a small proportion of recombinant (5%), Kappa (2%), and Alpha (1%). The viral clades G was found predominant for a year from initial days of pandemic in March, 2020 to January, 2021 which then subsequently evoluted to subclade GK (Delta B.1.617.2) and remained in circulation in CG till November, 2021. From December 2021, the GRA (Omicron B.1.1.529) variant had replaced GK to become the dominant strain and continues to predominate in present time. GRA clade is however continuously encompassing new recombinant strains, having various non-synonymous mutations especially in spike protein. The non-synonymous mutation P314L in ORF1b, S84L in ORF8 and D614G in spike protein were found as the pan mutation carried over from clade G to GRA. The continuous evolution in SARS-CoV2 warrants periodical geographic genomic surveillance monitoring to timely detect any new variants having the potential of causing future outbreak.