Preprint Article Version 2 Preserved in Portico This version is not peer-reviewed

Exploring COVID-19 Daily Records of Diagnosed Cases and Fatalities Based on Simple Non-parametric Methods

Version 1 : Received: 25 September 2020 / Approved: 26 September 2020 / Online: 26 September 2020 (12:31:57 CEST)
Version 2 : Received: 4 February 2021 / Approved: 8 February 2021 / Online: 8 February 2021 (15:54:23 CET)

A peer-reviewed article of this Preprint also exists.

Journal reference: IDR 2021
DOI: 10.3390/idr13020031

Abstract

Based on comprehensible non-parametric methods, estimates of crucial parameters that characterise the COVID-19 pandemic with a focus on the German epidemic are presented. Where appropriate, the estimates for Germany are compared with the results for seven other countries (FR, IT, US, UK, ES, CH, BR) to get an idea of the breadth of applicability and a relational understanding. Thereby, only prevalence data of daily reported new counts of diagnosed cases and fatalities provided by the Johns Hopkins University are used. Drawing on uncertain a priori knowledge is avoided. Specifically, we present estimates resulting from delay-time correlations for the duration from diagnosis to death being 13 days for Germany and Switzerland. The delay-time correlation applied to time series from other countries exhibit less pronounced peaks suggesting high variabilities for the corresponding time-to-death durations. With respect to the German data, the two time series of new cases and fatalities exhibit a strong coherence within the frequency range of interest, which backs our findings. Furthermore, based on the knowledge of this time lag between diagnoses and deaths, properly delayed asymptotic as well as instantaneous fatality-case ratios are calculated having superiority compared to the commonly published case-fatality rate. The temporal median of the instantaneous fatality-case ratio with proper delay of 13-days between cases and deaths for Germany turns out to be 0.02. Time courses of asymptotic fatality-case ratios are presented for other countries which substantially differ during the first half of the pandemic, however, converge to a narrow range with standard deviation 0.57% and mean 2.4%. Additionally, the time courses of instantaneous fatality-case ratios with optimal delay for the 8 exemplarily chosen countries are calculated and compared by means of the temporal medians. Similarly to the asymptotic fatality-case ratios, the differences are much smaller than expected from mass media reports. The basic reproduction number, R0, for Germany is estimated to be between 2.4 and 3.4. The uncertainty stems from uncertain knowledge of the generation time. A delay autocorrelation shows resonances at about 4 days and 7 days, where the latter resonance is at least partially attributable to the sampling process with weekly periodicity. The calculation of the basic reproduction number is based on an evaluation of cumulative numbers of cases yielding time-dependent doubling times as an intermediate step. This allows to infer to the reproduction number during the early phase of onset of the epidemic. In a second approach, the instantaneous reproduction number is derived from the incident (counts of new) cases and allows, in contrast to the first version, to infer to the temporal behaviour of the reproduction number during the later epidemic course. The time course of the reproduction number is compared to an alternative control measure given by the per capita growth, which largely confirms the conclusions drawn from the reproduction number. To conclude, by avoiding complicated parametric models we provide insights into basic features of the COVID-19 epidemic in an utmost transparent and comprehensible way. The perhaps most striking insight is that the fatality-case ratios do not differ between countries as much as previously suspected.

Keywords

SARS-CoV-2; corona virus; COVID-19; non-parametric model

Comments (1)

Comment 1
Received: 8 February 2021
Commenter: Hans H. Diebner
Commenter's Conflict of Interests: Author
Comment: We extended and applied our analysis to the "second wave" of the COVID-19 pandemic. Our previous estimates from the analysis of the first half of the pandemic could be confirmed. Due to the fact that we now have incidence time series twice as long as before, we were able to back our findings with respect to characteristic delay times previously found by means of delay-time correlation analyses, by an application of spectral analysis.

The most striking result from the extended analysis is the convergence of instantaneous fatality-case ratios (more reliable than the frequently used case-fatality rate) of 8 countries towards a narrow range of temporal medians from 0.013 to 0.03. Bearing in mind that the case-fatality rate depends on the differend countries' testing frequencies, it nevertheless indicates that the country-specific differences in mortality are far smaller than previously expected. Overall, we were able to confirm the feasibility of the proposed non-parametric method.
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