Meteorological factors and domestic new cases of coronavirus disease (COVID-19) in nine Asian cities: A time-series analysis

Zonglin He; Yiqiao Chin; Jian Huang; Yi He; Babatunde O. Akinwunmi; Shinning Yu; Casper J.P. Zhang; Wai-kit Ming

Moreover, under laboratory conditions with constant humidity and temperature, circadian and circannual rhythms in variation of susceptibility of hosts (mice) have been observed (13, 45) . Mice were substantially more susceptible to invasive pneumococcal disease in early morning hours than any other time of day(45), and more susceptible to influenza in winter than in summer (13) which was thought to be attributable to the daily and seasonal variation of melatonin (46). In addition, even in areas where many spend summers in air-conditioned spaces, marked annual variations in incidence constantly exist, and similar strains of virus appear almost simultaneously across vast stretches of oceans in areas of similar latitude around the globe (23, 24) . Therefore, although a higher temperature is associated with lower effectiveness of virus transmission, yet it does not necessarily suggest a lower chance for virus to survive. The natural fading out of the virus in summer is unlikely given the widespread use of air conditioners in developed areas and the dense population in the city area. Until an effective vaccine becomes widely available for the establishment of herd immunity and the discovery of efficient pharmaceutical therapies, strict public-health measures should be implemented, including social distancing, quarantine, tracing, facemask wearing, and promotion of hand washing.