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Geohealth ; : e2020GH000292, 2020 Oct 18.
Article in English | MEDLINE | ID: covidwho-1019739


The outbreak of coronavirus disease 2019 showed various transmission rate (R t ) across different regions. The determination of the factors affecting transmission rate is urgent and crucial to combat COVID-19. Here we explored variation of R t between 277 regions across the globe and the associated potential socioeconomic, demographic and environmental factors. At global scale, the R t started to decrease approximately two weeks after policy interventions initiated. This lag from the date of policy interventions initiation to the date when R t started to decrease ranges from 9 to 19 days, largest in Europe and North America. We find that proportion of elderly people or life expectancy can explain 50% of variation in transmission rate across the 277 regions. The transmission rate at the point of inflection (R I ) increases by 29.4% (25.2-34.0%) for 1% uptick in the proportion of people aged above 65, indicating elderly people face ~2.5 times higher infection risk than younger people. Air temperature is negatively correlated with transmission rate, which is mainly attributed to collinearities between air temperature and demographic factors. Our model predicted that temperature sensitivity of R I is only -2.7% (-5.2 - 0%) per °C after excluding collinearities between air temperature and demographic factors. This low temperature sensitivity of R I suggests that a warm summer is unlikely to impede the spread of COVID-19 naturally.

Innovation (N Y) ; 2(1): 100071, 2021 Feb 28.
Article in English | MEDLINE | ID: covidwho-978457


The COVID-19 outbreak has already become a global pandemic and containing this rapid worldwide transmission is of great challenge. The impacts of temperature and humidity on the COVID-19 transmission rate are still under discussion. Here, we elucidated these relationships by utilizing two unique scenarios, repeated measurement and natural experiment, using the COVID-19 cases reported from January 23 - February 21, 2020, in China. The modeling results revealed that higher temperature was most strongly associated with decreased COVID-19 transmission at a lag time of 8 days. Relative humidity (RH) appeared to have only a slight effect. These findings were verified by assessing SARS-CoV-2 infectivity under the relevant conditions of temperature (4°C-37°C) and RH (> 40%). We concluded that temperature increase made an important, but not determined, contribution to restrain the COVID-19 outbreak in China. It suggests that the emphasis of other effective controlling polices should be strictly implemented to restrain COVID-19 transmission in cold seasons.