The explanatory power, i.e., coefficient of determination (R2), of the model as the COVID-19 pandemic progressed, reaching >70% in April 2020 (Fig 5A). The number of days from case onset had some explanatory power (> 20%) in January, 2020, but this factor quickly lost its influence as the pandemic progressed (Fig 5B). As the influence of this factor waned, other variables (related to climate, human mobility, and host susceptibility to COVID-19) exhibited the increasing explanatory powers (Fig 5B). After April 2020, the explanatory power of variables related to human mobility and host susceptibility to COVID-19 rapidly decreased. After this, the explanatory power of human population and climate factors increased. These results demonstrate that the impact of virus dispersability between/within regions was predominant in the beginning stage of the pandemic (Fig 5).