The shocks have come one after another: Islamic State killings of civilians in Brussels and Nice. A deadly outburst of terrorism in Germany. A fresh terror-linked atrocity in a small French town. Warnings abound that more may be on the way.

The surge of attacks in Europe has raised questions over whether a potentially durable new threat to stability is settling in. The political challenges for Europe’s leaders are stark, and the impact on the region’s economy may be just as profound.

“We are experiencing a structural change, a phenomenon of war on our doorstep that didn’t exist before,” said Georges Panayotis, the president of the MKG Group, a tourism consulting company based in Paris. “If it’s not resolved, the problem will continue.”

The effects of that shift on businesses, large and small, have been deep.