The SARS-CoV-2 genome size is around 29.9kb, which is in the same order of magnitude as other RNA viruses. Its evolutionary rate is about 1.1×10?3 substitutions per site per year, even lower than some influenza A viruses which have a rate between 1.8 × 10?3 to 2.2 × 10?3. Virus genome sequencing helps response to COVID-19 by identifying mutations, variants and strains to understand transmission and develop vaccines and treatments.