Due to the sharp rise in the number of infections and the resulting increasing difficulties in tracing infection chains, the Czech government also set all four districts in the Elbe/Labe Euroregion (Ústí, Děčín, Teplice and Litoměřice) to the second highest corona warning level on September 18th. According to the traffic light symbolism applied there, they therefore appear yellow.
The number of new infections in the last 7 days, which is important for German decision makers, is also very high. In the district of Ústí it was 137 - calculated per 100,000 inhabitants. In Germany, the first measures are taken from 35 onwards, from 50 it's getting serious.
Due to these developments, it is expected that the whole of the Czech Republic will soon be declared a risk area by the Robert Koch Institute. Travellers from the Czech Republic would then have to be quarantined in Germany, including return travellers who have only been in the Czech Republic for a short time.
More about the current corona rules in Saxony and the Czech Republic can be found here.