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

Researchers have long been investigating how meteorological factors affect the viral infectivity, where the GAM has been frequently used, as it allows smooth components to be estimated for time, meteorological factors and other covariates, together with a non-smoothed period effect. Experiments in the last century reported that the influenza virus is more stable in cool and dry air (15, 16) . And with increasing temperature, the viability of the influenza virus in aerosol or droplets(38), and the aerosol transmission diminishes (27) . Lowen et al. reported that aerosol transmission of influenza between Guinea pigs was completely blocked at temperature higher than 30°C despite evidence of continuous viral shedding from infectious individuals; nevertheless, the direct contact transmission was not influenced, which was equally efficient at 30° C and 20° C (19) . Chan et al. reported that the viability of SARS virus was rapidly lost (>3 log 10) at high temperatures (38 • C) and high relative humidity (>95%) (31) . The better stability of the SARS coronavirus at low temperatures and low humidity environment might facilitate its transmission in the community in subtropical areas (such as Hong Kong) during the spring and in air-conditioned environments. This might also explain why some Asian countries in tropical areas (such as Malaysia, Indonesia or Thailand) with high temperatures and high relative humidity environment did not have major community outbreaks of SARS. However, such an explanation is not currently convincing regarding the results in the present study, where the increase of the temperature increases the daily new cases of COVID-19 in some of the investigated communities. The high temperature and high relative humidity in the tropical Asian countries like Singapore, and Malaysia also seems to have little influence on the expanding daily new cases ( Figure 3 ). However, this could have been confounded by multiple factors.