Correct Testing and Quarantine Measures Are Missing

The interesting analysis (1) needs to be expanded to include a decisive aspect. Namely, what are the sources of infection? The (inadequate) test method makes it obvious that these are the mostly younger (<60 years old) travelers who returned after the summer and autumn holidays. After short vacations of up to a week, around 50–100% of the asymptomatic infected individuals were able to enter the country undetected. The newly infected individuals who tested positive (who were, according to the Robert Koch Institute [RKI], mostly returning travelers) were initially easy to control using test, trace, and isolate (TTI). However, incoming travelers with false-negative results who remained undetected acted as drivers of infection and unknowingly formed the gateway for SARS-CoV-2, which subsequently spread to the second wave with a high number of unreported cases.

This virus introduction would have been effectively contained through adequate testing of all incoming travelers or, alternatively, by not travelling (Christmas holidays, December 2020/January 2021). As expected, there was a renewed increase of new infections at the end of November/beginning of December 2020, despite lockdown measures, due to returning travelers because correct test quarantine measures were not carried out. The resulting very high number of unreported cases prevents TTI and requires targeted, consistent measures to prevent the increase in new infections, making an undifferentiated lockdown method that causes collateral damage superfluous.