Influence of Absolute Humidity and Population Density on COVID-19 Spread and Decay Durations: Multi-prefecture Study in Japan
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This study analyzed the spread and decay durations of the COVID-19 pandemic in different prefectures of Japan. In Japan, in addition to affordable wide coverage health insurance systems, no medical collapse was observed, making accurate comparisons between prefectures possible. For the 19 prefectures included in this study that had daily maximum confirmed cases exceeding ten, the confirmed cases increased and decreased exponentially in the spread and decay durations in most of the prefectures. A good correlation was observed between the spread and decay durations (R2=0.37). However, some exceptions were observed in prefectures that are adjacent to primary prefectures (e.g., Tokyo, Osaka, Aichi, and Fukuoka) and in areas where people returned from foreign countries, which were defined origins of cluster infections. Excluding these prefectures, population density is shown to be the primary factor affecting spread and decay patterns, with correlations of 0.52 and 0.76, respectively. The absolute humidity also affected the spread duration (R2=0.40). These findings could be useful for intervention planning during potential future pandemics, including a second COVID-19 outbreak.
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