As the new coronavirus jumped from country to country in recent weeks, the responses of their governments to the pandemic have highlighted how much national borders still matter in what seemed to be an increasingly borderless world.

New travel and trade restrictions are popping up daily, policies that seemed unthinkable until recently and that disrupt economies used to global supply chains. A shortage of pharmaceutical components produced in China and other export curbs are already making the fight against the virus and other diseases more difficult. The impact of these developments is likely to outlast the pandemic itself, reshaping global trade flows and domestic politics in many democracies.

“This crisis favors all the populist and nationalist forces that have long called for reinforcing borders. It is a true gift for them,” said Nicolas Tenzer, chair of the Cerap think tank in Paris. “At the same time, without yielding to the idea of de-globalization, this is going to stimulate a real reflection on the need not to be too economically dependent on some powers, such as China.”

In the European Union, where borders have seemed largely irrelevant since the Schengen treaty in 1995 removed immigration checks between nations, the shock of the coronavirus pandemic has closed some of these borders again—shutdowns not seen since World War II.

Austria and Slovenia on Tuesday banned entry to Italians, unless they have a special medical permission. Those are frontiers that many thousands used to drive or walk across every day to shop, work or attend schools, just as easily as crossing between New York state and Connecticut. Slovakia declared its borders closed to all travelers who can’t show proof of residency. The Czech Republic on Thursday followed suit by banning travelers from fifteen virus-hit countries, including neighboring Germany.