that ( i ) SARS - CoV-2 genomes are overall conserved under purifying selection .
( ii ) Ongoing positive selection is actively driving the evolution of specific genes .
Interrogating 22,078 SARS - CoV-2 genome sequences of 84 countries , we demonstrate with convincing evidence that ( i ) SARS - CoV-2 genomes are overall conserved under purifying selection .
( ii ) Ongoing positive selection is actively driving the evolution of specific genes .