A delayed modulation of solar ultraviolet radiation on the COVID-19 transmission reflects an incubation period

Laboratory experiments have revealed the meteorological sensitivity of the coronavirus disease 2019 (COVID-19) virus. However, no consensus has been reached about how outdoor meteorological conditions modulate the virus transmission as it is also constrained by non-meteorological conditions. Here, we find that statistically, non-meteorological factors constrain the growth rate of cumulative confirmed cases least when the cases in a country arrive around 1300–3200. The least-constrained growth rate correlates with the ultraviolet flux and temperature significantly (correlation coefficients r =-0.55 ± 0.09 and -0.40 ± 0.10 at p < 0.01, respectively), but not with precipitation, humidity, and wind. The ultraviolet correlation exhibits a delay of about seven days, providing a meteorological measure of the incubation period. Our work reveals a seasonality of COVID-19 and a high risk of a pandemic resurgence in winter, implying a need for seasonal adaption in public policies.