Ongoing Global and Regional Adaptive Evolution of SARS-CoV-2

Area of Science:

• Virology
• Evolutionary Biology
• Genomics

Background:

• Understanding SARS-CoV-2 evolution is critical for managing the COVID-19 pandemic.
• Analysis of viral genome sequences provides insights into evolutionary trends and selection pressures.

Approach:

• Analyzed over 300,000 high-quality SARS-CoV-2 genome sequences up to January 2021.
• Investigated patterns of selection, phylogenetic partitioning, and geographic spread.
• Examined key mutations in the spike protein and nucleocapsid protein.

Key Points:

• Purifying selection dominates SARS-CoV-2 evolution, with specific sites under positive selection.
• Positively selected sites in the spike protein's receptor-binding domain and nucleocapsid protein's NLS region show epistatic interactions.
• Four distinct periods of viral evolution and global partitioning were identified, marked by diversification, homogenization (D614G spread), NLS variant rise, and regional diversification with antibody-evading mutations.

Conclusions:

• Key mutations in SARS-CoV-2, especially in the spike and nucleocapsid proteins, drive viral evolution and diversification.
• The identified evolutionary periods and selection patterns offer insights into pandemic dynamics and the emergence of significant variants.
• Ongoing regional diversification, potentially leading to speciation, highlights the need for continuous genomic surveillance and understanding of viral evolution.