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. 2021 Dec;63(8):1623-1632.
doi: 10.1002/bimj.202100125. Epub 2021 Aug 10.

A statistical model for the dynamics of COVID-19 infections and their case detection ratio in 2020

Marc Schneble  1 , Giacomo De Nicola  1 , Göran Kauermann  1 , Ursula Berger  2
Affiliations

A statistical model for the dynamics of COVID-19 infections and their case detection ratio in 2020

Marc Schneble et al. Biom J. 2021 Dec.

Abstract

The case detection ratio of coronavirus disease 2019 (COVID-19) infections varies over time due to changing testing capacities, different testing strategies, and the evolving underlying number of infections itself. This note shows a way of quantifying these dynamics by jointly modeling the reported number of detected COVID-19 infections with nonfatal and fatal outcomes. The proposed methodology also allows to explore the temporal development of the actual number of infections, both detected and undetected, thereby shedding light on the infection dynamics. We exemplify our approach by analyzing German data from 2020, making only use of data available since the beginning of the pandemic. Our modeling approach can be used to quantify the effect of different testing strategies, visualize the dynamics in the case detection ratio over time, and obtain information about the underlying true infection numbers, thus enabling us to get a clearer picture of the course of the COVID-19 pandemic in 2020.

Keywords: COVID-19; case detection ratio; dark figure of infections; generalized additive models; penalized splines.

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Conflict of interest statement

The authors have declared no conflict of interest.

Figures

FIGURE 1
FIGURE 1
Raw data: registered cases of COVID‐19 infections and registered fatal cases on a weekly basis for Germany. Top figure: Absolute numbers on a log‐scale stratified by age group. Bottom figure: Case fatality ratios (= fatal cases / registered cases) stratified by age group
FIGURE 2
FIGURE 2
Dynamics of the true infection numbers on the log‐scale for different age groups: The smooth random effects Vt. The shaded areas represent 95% confidence bands
FIGURE 3
FIGURE 3
Dynamics in the case‐detection ratio for different age groups: The normalized time‐varying coefficients βt. The function values on the exp‐scale (right y‐axes) are the relative change in the case‐detection ratio (CDR) with respect to calendar week 10
See this image and copyright information in PMC

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