WORLDWIDE CASE FATALITY RATIO OF COVID-19 OVER TIME

  1. Rohan Chaubal
  2. Sadhana Kannan
  3. Navin Khattry
  4. Sudeep Gupta

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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.

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    SciScore for 10.1101/2020.10.04.20206599: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    NIH rigor criteria are not applicable to paper type.

    Table 2: Resources

    Software and Algorithms
    SentencesResources
    Data analysis: Data analysis was performed using custom python scripts, GraphPad Prism version 8.02 for Windows, GraphPad Software, La Jolla California USA and Microsoft Excel (2019), Microsoft Corporation, Redmond, USA.
    python
    suggested: (IPython, RRID:SCR_001658)
    GraphPad Prism
    suggested: (GraphPad Prism, RRID:SCR_002798)
    GraphPad
    suggested: (GraphPad Prism, RRID:SCR_002798)
    Microsoft Excel
    suggested: (Microsoft Excel, RRID:SCR_016137)

    Results from OddPub: Thank you for sharing your code and data.

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    There are some limitations of our analysis. We did not account for time- or severity-dependent reporting of cases and also for the time-lag in outcomes. It is possible that COVID-19-related deaths have been underreported in some parts of the world and that the actual CFR is higher than our estimates. We did not have access to patient-level data and data of such granularity may never become available for such a large number of cases and deaths. Therefore, we have been unable to provide ‘adjusted’ CFR after accounting for the distribution of variables. The correlation between CFR and health and social parameters could possibly be masked or confounded because the latter were available at the country-level with likely intra-country variation. In summary, our analysis confirms that COVID-19 is a severe disease in a considerable minority of patients, its CFR has gradually increased in many parts of the world, and, given the large number of cases, is likely to result in high absolute number of deaths unless an effective vaccine or treatment is developed. Our analysis also indicates that the herd immunity argument is likely inappropriate and will possibly result in a high number of fatalities. Governments and public health authorities should consider the CFR among clinically presenting cases and plan acute care capacity accordingly.

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

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  2. Version published to 10.1101/2020.10.04.20206599v1 on medRxiv