Factors associated with country-variation in COVID-19 morbidity and mortality worldwide: an observational geographic study

Background: The world is threatened by the outbreak of coronavirus disease 19 (COVID-19) since December 2019. The number of cases and deaths increased dramatically in some countries from March 2020. The objective of our study was to examine potential associated factors with country-variation in COVID-19 morbidity and mortality in the world. Methods: We performed a retrospective geographic study including all countries with the most recent available data on free access on the web. We analyzed univariate and multivariable correlation between both the number of reported cases and deaths by country and demographic, socioeconomic characteristics, lockdown as major control measure, average annual temperature and relative humidity. We performed simple linear regression, independent t test and ANOVA test for univariate analyses and negative binomial regression model for multivariable analyses. Results: We analyzed data of 186 countries from all world regions. As of 13th April 2020, a total of 1 804 302 COVID-19 cases and 113 444 deaths were reported. The reported number of COVID-19 cases and deaths by countries was associated with the number of days between the first case and lockdown, the number of cases at lockdown, life expectancy at birth, average annual temperature and the socio-economic level. Countries which never implemented BCG vaccination reported higher mortality than others. Conclusions: The pandemic is still ongoing and poses a global health threat as there is no effective antiviral treatment or vaccines. Thus, timing of control measure implementation is a crucial factor in determining the spread of the epidemic. It should be a lesson for this pandemic and for the future.