Evidence that higher temperatures are associated with lower incidence of COVID-19 in pandemic state, cumulative cases reported up to March 27, 2020

Michael Triplett

Population values were assigned locations for case-mapping by taking the average (middle) of each nation's most extreme latitudes and longitudes (i.e. the latitudes and longitudes of each nation's northern-, eastern-, southern-and western-most points). For nations in the western hemisphere above 40 degrees latitude at center, and for nations in the eastern hemisphere above 60 degrees latitude at center, populations were assumed to be concentrated near the southernmost border. Fig. 1 shows how populations were represented from -65 o to 65 o degrees latitude Global gridded daily maximum surface temperature data, with 0.5 o spatial resolution, for the dates from February 29 to March 14, 2020, were accessed from the US National Oceanic and Atmospheric Administration (NOAA), Earth system research Laboratory (ESRL), Physical Sciences Division website (ftp://ftp.cdc.noaa.gov/Datasets/cpc_global_temp/) 3 . Dates two weeks prior to respective case dates were chosen to account for 14 days between transmission and case confirmation. As shown in fig. 2 , recorded mean maximum temperature values were averaged across each reported latitude for each day and assigned to reporting nations based on modeled population latitudes. For data reported March 27, 2020, multiple linear regression analysis 12 was then performed for confirmed cases at the national level using estimated populations and mean maximum temperatures at assigned latitudes as predictors. Case data was transformed using the Box-Cox 14 method with λ = 0. To reduce variance, populations were then binned 11 into 5 o latitude and temperature ranges set at 2.5 o intervals. Multiple linear regression was then performed for confirmed cases binned by latitude, again using population and mean maximum temperature as predictors, with and without a categorical variable describing bins above and below 30 o latitude. Confirmed case data binned by latitude was transformed, again using the Box-Cox method, with λ = 0.212028 for analysis including the categorical variable and λ = 0 for analysis without. Nonlinear regression analysis 13 was also performed, without transformation, for case rates binned by mean maximum temperature at latitude, using temperature as the only predictor.