Progressing adaptation of SARS-CoV-2 to humans

Abstract

The second and subsequent waves of the coronavirus disease (COVID-19) have caused problems worldwide. Here, using objective analysis, we present the changes that occurred in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The virus has mutated in three major directions, resulting in three groups to date. The basic viral genome was identified in April and shared across all continents. However, the virus continued to mutate independently in each country after the closure of borders. Some variants with greater infectivity replaced the earlier ones and caused second waves of the disease. Some of them slowly entered other countries and caused epidemics. Going forward, these viruses could also serve as sources of further mutations.