The German health authorities are expecting a rapid spread of the new coronavirus in the country, at a time when at least 10 new cases of infection have been confirmed and the search for further infections continued into Friday.
Five fresh cases were reported in the state of North Rhine-Westphalia.
Around 300 people who took part in a carnival at the beginning of the week in Gangelt on the Dutch border were asked to report to the authorities.
In the south-western state of Baden-Württemberg, a group of four infected persons is being monitored.
The military authorities are also checking up on their troops after a soldier was infected in Koblenz.
“We are at the start of a coronavirus epidemic in Germany,” the health minister Jens Spahn declared on Wednesday evening in Berlin. “To a certain extent, chains of infection would not be able to be retraced, which is novel.”