Bloomberg reports that Chancellor Angela Merkel warned that aggressive coronavirus mutations will gain the upper hand in Germany sooner or later, threatening to destroy progress made in containing the pandemic.

Europe’s largest economy needs to maintain tight controls even as contagion rates steadily decline and immunizations slowly ramp up, Merkel said Thursday. The fast-spreading British variant is already in the country, she added.

“Experts tell us that it will be only a matter of time until these mutations will become dominant,” Merkel said in a speech to parliament in Berlin. “We know that the danger of mutations can again wreck our successes.”