Investigating the Dark Figure of COVID-19 Cases in Austria: Borrowing From the Decode Genetics Study in Iceland

Abstract

The number of undetected cases of SARS-CoV-2 infections is expected to be a multipleof the reported figures mainly due to the high ratio of asymptomatic infections and tolimited availability of trustworthy testing resources. Relying on the deCODE study inIceland, which offers large scale testing among the general population, we investigate themagnitude and uncertainty of the number of undetected cases COVID-19 cases in Austria.We formulate several scenarios relying on data on the number of COVID-19 cases whichhave been hospitalized, in intensive care, as well as on the number of deaths and positivetests in Iceland and Austria. We employ frequentist and Bayesian methods for estimatingthe dark figure in Austria based on the hypothesized scenarios and for accounting for theuncertainty surrounding this figure.Using data available on April 1, 2020, our study contains two main findings: First, wefind the estimated number of infections to be on average around 8.35 times higher thanthe recorded number of infections. Second, the width of the uncertainty bounds associatedwith this figure depends highly on the statistical method employed. At a 95% level, lowerbounds range from 3.96 to 6.83 and upper bounds range from 9.82 to 12.61. Overall, ourfindings confirm the need for systematic tests in the general population of Austria.