The foreign ministry said “the trend in the number of new infections and new deaths has been rising again since the end of July, particularly in the Antwerp province”.
“The number of new infections has passed 50 cases per 100,000 residents.”
That prompted Germany's disease control agency, the Robert Koch Institute “to declare this area a risk zone” the ministry added.
“Due to that, there is a requirement for quarantine in Germany, that one can avoid through a negative COVID-19 test.”
The number of coronavirus patients admitted to Belgium's intensive care units has doubled in a month and the epidemic is spreading “intensively”, health officials said Monday.
Belgium suffered one of the highest per capita rates of infection at the height of COVID-19's progress through Europe but began easing lockdown measures in May after the disease peaked.
Now, cases are climbing once again and the country of 11 million has postponed plans to further ease anti-virus measures, while imposing tougher controls in the port city of Antwerp.
Out of a population of around 11 million, 9,852 have died.
Anyone currently arriving in Germany from areas considered to be at high risk must produce a negative coronavirus test or go into quarantine for 14 days.
In a blow to tourism in Spain, Germany last week added three northern Spanish regions to its high-risk destination list.
Germany, which has seen just over 9,000 COVID-19 deaths, has drawn up strict rules to limit transmission of the new coronavirus, with cases rising above 500 per day in recent weeks.