WORLDWIDE CASE FATALITY RATIO OF COVID-19 OVER TIME

ABSTRACT Background The case fatality ratio (CFR) of coronavirus disease 2019 (COVID-19) has been reported to be variable among different countries and regions but few analyses have tracked this ratio worldwide over time. Methods The primary objective was to assess the time-course evolution of CFR of COVID-19 in all countries with available data and secondary objective was to evaluate associations between country-wise CFR and country-level health, human development, demographic and economic parameters. Day-wise data of COVID-19 cases and deaths for each country was extracted from a public repository and countries with at least 1000 cases on cutoff date were clustered by unsupervised k-means on the basis of deaths per 100000 population (DP100K). Day-wise CFR (cumulative deaths divided by cumulative cases, multiplied by 100) for each country and cluster (country group) was plotted as time-series and country-level parameters were tested for association with CFR using weighted multiple linear regression. Results On September 24, 2020 there were 32140504 cumulative COVID-19 cases and 981792 deaths reported from 184 countries for a worldwide CFR of 3.06 % (95%CI 3.05 -3.07). Unsupervised k-means clustering in 157 countries with at least 1000 reported cases resulted in Clusters (country groups) A, B, C, D and E with centroid DP100K and CFR of 0.100 and 2.51 (95% CI 2.42-2.61), 0.503 and 2.28 (95% CI 2.23-2.33), 1.816 and 1.73 (95% CI 1.71-1.75), 7.395 and 1.76 (95% CI 1.75-1.76), and 36.303 and 3.82 (95% CI 3.82-3.83), respectively. In a log-log analysis DP100K and CFR were significantly positively correlated (R=0.3570, p<0.001) with each other. All country groups and majority of included countries showed a pattern of gradually increasing CFR from the beginning of pandemic, followed by a plateau and then a steady decline in CFR. Among 10 country-level parameters, GDP per capita (β=-0.483, p=0.000), hospital beds per population (β=-0.372, p<0.001), mortality from air pollution (β=-0.487, p=0.003) and population density (β=-0.570, p< 0.000) were significantly negatively associated while maternal mortality ratio (β=0.431, p=0.000) and age (β=0.635, p<0.000) were positively associated with CFR. Conclusions The CFR of COVID-19 has gradually increased over time in majority of countries at various stages of the pandemic, followed by a plateau and a steady decline. Population level COVID-19 mortality burden and CFR are significantly positively associated with each other.