Nonlinear modulation of COVID-19 transmission by climate conditions.

COVID-19 is spreading rapidly worldwide, posing great threats to public health and economy. This study aims to examine how the transmission of COVID-19 is modulated by climate conditions, which is of great importance for better understanding of the seasonal feature of COVID-19. Constrained by the accurate observations we can make, the basic reproduction numbers ( ) for each country were inferred and linked to temperature and relative humidity (RH) with statistical analysis. Using as the measure of COVID-19 transmission potential, we find stronger transmission of COVID-19 under mildly warm (0°C < < 20°C) and humid (RH > 60%) climate conditions, while extremely low ( < -2°C) and high ( > 20°C) temperature or a dry climate (RH < 60%) weakens transmission. The established nonlinear relationships between COVID-19 transmission and climate conditions suggest that seasonal climate variability may affect the spread and severity of COVID-19 infection, and temperate coastal regions with mildly warm and humid climate would be susceptible to large-scale outbreaks.