Preliminary evidence that higher temperatures are associated with lower incidence of COVID-19, for cases reported globally up to 29th February 2020

Melanie Bannister-Tyrrell; Anne Meyer; Celine Faverjon; Angus Cameron

Pandemic COVID-19, caused by a beta-coronavirus named SARS-CoV-2 first identified in Wuhan, China [1] , has spread rapidly, particularly in temperate regions in the northern hemisphere [2] . The number of cases reported in countries in tropical regions, most of which are low-and middle-income countries (LMICs) with weaker detection and response capacity [3] , is lower [2] . There has been much speculation about whether warming temperatures with the onset of spring and summer will contribute to decreased transmission in the northern hemisphere, as is observed for many viral respiratory infections [4] . This would also have implications for the risk of spread in temperate regions in the southern hemisphere at the onset of winter, and for tropical regions where the vast majority of LMICs are located. Higher temperatures were shown to have a protective effect against transmission of severe acute respiratory syndrome (SARS) in 2002-2003 [5] , possibly due to the decreased survival of the SARS-CoV on surfaces at higher temperatures [6] . Decreased aerosol spread at higher temperatures is another possible mechanism, as observed for human influenza viruses [7] . This study aimed to provide preliminary data on whether there may be seasonal variation in COVID-19 incidence, in sub-national regions that have reported at least one confirmed COVID-19 case.