Wavelet analysis of COVID-19 pandemic

Seven to eight COVID-19 epidemic waves have been observed in Japan as of December 2022. By performing a wavelet analysis using publicly available data on the number of COVID-19 positive individuals reported and calculating the phase difference between the infection waves, the spatial and temporal characteristics of the spread of infection were examined. In Japan's prefectural analysis, the spread of infection from the large cities of Tokyo, and Osaka to the surrounding areas and to the Sanyo and Kyushu regions was indicated. On the other hand, it was found that the standard deviation of the phase difference in other prefectures was large across zero phase difference. The former is considered to represent the regularity involving with the spread of COVID-19, while the latter is considered to represent its stochastic aspect.