Five years of SARS-CoV-2 evolution: variants, mechanisms, and public health challenges

This is the authors' abstract. We don't add key points for this paper.

Since its emergence in 2019, SARS-CoV-2 has shown remarkable evolutionary plasticity, profoundly shaping the course of the COVID-19 pandemic. This review summarizes key evolutionary milestones from 2019 to 2025, highlighting mechanisms such as point mutations, positive selection, recombination, and evolution in immunocompromised hosts. Early mutations, including D614G, increased viral infectivity, while later variants such as Alpha, Delta, and Omicron significantly altered transmissibility and immune evasion. Omicron diversification generated multiple sublineages (BA.5, XBB, JN.1, KP.2), many displaying convergent evolution and sustained global spread. Although disease severity has generally decreased due to widespread hybrid immunity, challenges such as long COVID, vaccine escape, and global health inequities persist. Updated vaccines continue to protect against severe disease, although their effectiveness against symptomatic infection is reduced. These findings underscore the need for continued genomic surveillance, equitable access to medical interventions, and preparedness for emerging variants and future public health challenges. This narrative review was developed through literature searches in PubMed, Scopus, Web of Science, and Google Scholar, covering publications from 2019 to 2025.