  The transmission and evolution of severe acute respiratory syndrome
coronavirus 2 (SARS-CoV-2) are of paramount importance to the controlling and
combating of coronavirus disease 2019 (COVID-19) pandemic. Currently, near
15,000 SARS-CoV-2 single mutations have been recorded, having a great
ramification to the development of diagnostics, vaccines, antibody therapies,
and drugs. However, little is known about SARS-CoV-2 evolutionary
characteristics and general trend. In this work, we present a comprehensive
genotyping analysis of existing SARS-CoV-2 mutations. We reveal that host
immune response via APOBEC and ADAR gene editing gives rise to near 65\% of
recorded mutations. Additionally, we show that children under age five and the
elderly may be at high risk from COVID-19 because of their overreacting to the
viral infection. Moreover, we uncover that populations of Oceania and Africa
react significantly more intensively to SARS-CoV-2 infection than those of
Europe and Asia, which may explain why African Americans were shown to be at
increased risk of dying from COVID-19, in addition to their high risk of
getting sick from COVID-19 caused by systemic health and social inequities.
Finally, our study indicates that for two viral genome sequences of the same
origin, their evolution order may be determined from the ratio of mutation type
C$>$T over T$>$C.
