Convergent movement of COVID-19 outbreak in Japan based on SIR model

The infection dynamics of COVID-19 show frequent phases in which the infection spreads rapidly, resembling explosive infection. However, despite the repeated increases and decreases, there is a process of convergence even within a relatively short period of time. While it is obvious that the growth rate of the cumulative number of infected people slows down as it increases, considering the infectious disease process, we also observe a slowdown in the growth rate of the net number of infected people. Moreover, there exists a special type of convergence whereby areas with initially many infected people exhibit low rates of increase in the numbers of infected people subsequently. This paper uses prefectural panel data from Japan through March 2021 to confirm the convergence process.