ORCID

Abstract

BACKGROUND: The spread of coronavirus disease 2019 (COVID-19) varied among countries. The spatiotemporal trends of COVID-19 in Japan remain understudied. Therefore, this study aimed to conduct a detailed investigation of the spatiotemporal evolution of infections/deaths across prefectures in Japan, to analyze the changing patterns of COVID-19 circulation in metropolitan and nonmetropolitan areas.

METHODS: We extracted data from nationally represented open-source data from January 15, 2020, to May 9, 2023, and we calculated the incidence rate of infection and the mortality. Further the ratios were obtained by dividing those rates in prefectural level by those in national level to make them comparable across country. Then, the spatiotemporal trends of COVID-19 were depicted via heatmaps. A Poisson regression model was used to compare the incidence rate ratios (IRRs) of infection and death between nonmetropolitan and metropolitan prefectures.

RESULTS: During the study period, Japan experienced eight waves of COVID-19 resulting in 33,738,398 confirmed infections and 74,688 deaths. Both infections and deaths increased significantly overtime. Transmission was initially concentrated in metropolitan prefectures. Nonmetropolitan prefectures were protected and had lower numbers of infections and deaths through June 2022. Thereafter, COVID-19 became more widespread, with more localized surges in nonmetropolitan prefectures. Eventually, during the eighth wave (October 16, 2022-May 9, 2023), there was a marked increase in the IRR in nonmetropolitan prefectures reaching 1.25 (95 % confidence interval (CI), 1.15-1.34) for infection and 1.38 (95 % CI, 1.16-1.65) for death.

CONCLUSIONS: In Japan, COVID-19 transmission was suppressed for the first 2 years of the pandemic, especially in nonmetropolitan prefectures, but the trends changed over time, and more infections and deaths were observed from late 2022 in nonmetropolitan prefectures. These findings underscore the importance of addressing the geographical disparities that likely exist between metropolitan and nonmetropolitan prefectures Delaying large surges in nonmetropolitan prefectures may be an important takeaway that could aid in the future management of major infectious disease outbreaks.

DOI

10.1016/j.jiph.2025.102704

Publication Date

2025-02-14

Publication Title

Journal of Infection and Public Health

Volume

18

Issue

5

ISSN

1876-0341

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

First Page

102704

Last Page

102704

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