Covid 19



Spotlight on the dark figure: Exhibiting dynamics in the case detection ratio of COVID-19 infections in Germany

Autoren/Herausgeber: Schneble
De Nicola
Erschienen: 2021
Publikationsart: Publikationen

The case detection ratio of COVID-19 infections varies over time due to changing testing capacities, modified testing strategies and also, apparently, due to the dynamics in the number of
infected itself. In this paper we investigate these dynamics by jointly looking at the reported
number of detected COVID-19 infections with non-fatal and fatal outcomes in different age
groups in Germany. We propose a statistical approach that allows us to spotlight the case
detection ratio and quantify its changes over time. With this we can adjust the case counts
reported at different time points so that they become comparable. Moreover we can explore the
temporal development of the real number of infections, shedding light on the dark number. The
results show that the case detection ratio has increased and, depending on the age group, is four
to six times higher at the beginning of the second wave compared to what it was at the peak of
the first wave. The true number of infection in Germany in October was considerably lower as
during the peak of the first wave, where only a small fraction of COVID-19 infections were detected. Our modelling approach also allows quantifying the effects of different testing strategies
on the case detection ratio. The analysis of the dynamics in the case detection rate and in the
true infection figures enables a clearer picture of the course of the COVID-19 pandemic.

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