Meteorological factors and COVID-19 incidence in 190 countries: An observational study

Abstract

Novel corona virus disease 2019 (COVID-19), which first emerged in December 2019, has become a pandemic. This study aimed to investigate the associations between meteorological factors and COVID-19 incidence and mortality worldwide. This study included 1,908,197 confirmed cases of and 119,257 deaths from COVID-19 from 190 countries between 23 January and 13 April, 2020. We used a distributed lag non-linear model with city-/country-level random intercept to investigate the associations between COVID19 incidence and daily temperature, relative humidity, and wind speed. A series of confounders were considered in the analysis including demographics, socioeconomics, geographic locations, and political strategies. Sensitivity analyses were performed to examine the robustness of the associations. The COVID-19 incidence showed a stronger association with temperature than with relative humidity or wind speed. An inverse association was identified between the COVID-19 incidence and temperature. The corresponding 14-day cumulative relative risk was 1.28 [95% confidence interval (CI), 1.20-1.36] at 5 °C, and 0.75 (95% CI, 0.65-0.86) at 22 °C with reference to the risk at 11 °C. An inverse J-shaped association was observed between relative humidity and the COVID-19 incidence, with the highest risk at 72%. A higher wind speed was associated with a generally lower incidence of COVID-19, although the associations were weak. Sensitivity analyses generally yielded similar results. The COVID-19 incidence decreased with the increase of temperature. Our study suggests that the spread of COVID-19 may slow during summer but may increase during winter.

Keywords: COVID-19 incidence; COVID-19 mortality; Meteorology; Relative humidity; Temperature; Wind speed.

Graphical abstract

Fig. 1

Spatial distribution of cumulative confirmed cases of COVID-19 and meteorological monitoring stations worldwide as of 13 April, 2020. Green points represent the locations of meteorological monitoring stations and colours represent the number of cumulative confirmed cases of COVID-19 as of 13 April, 2020. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 2

Overall association of the cumulative risk of COVID-19 incidence with temperature, relative humidity, and wind speed. Red lines represent the estimated cumulative relative risks of COVID-19 incidence with shaded bands as 95% confidence intervals. A, B, and C represent the associations of the 14-day cumulative risk of COVID-19 incidence with daily temperature, relative humidity, and wind speed, respectively. The corresponding reference levels were 11 °C, 71% and 3 m/s, respectively. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 3

Associations of the daily risk of COVID-19 incidence with the 25^th, 50^th and 75^th percentiles of meteorological factors over a 14 consecutive days. Red lines represent the estimated relative risks (RRs) of COVID-19 incidence with shaded bands as 95% confidence intervals. A, B, and C show the relative risk of COVID-19 incidence by comparing the 25^th (5.0 °C), 50^th (11.0 °C), and 75^th (22.0 °C) percentiles of daily average temperature to median value (7 °C), respectively. D, E, and F indicate the RRs of COVID-19 incidence by comparing the 25^th (59%), 50^th (71%) and 75^th (79%) percentiles of daily relative humidity to the median humidity (71%), respectively. G, H, and I represent the RRs of COVID-19 incidence by comparing the 25^th (2 m/s), 50^th (3 m/s), and 75^th (4 m/s) percentiles of daily wind speed to the median wind speed (3 m/s), respectively. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)