For a fleeting period, Europe nearly resembled its old self, with people zipping around without restrictions or mandatory quarantines. With coronavirus cases rising again, governments across the continent are abruptly rethinking the wisdom unrestricted travel, while reinstituting quarantines and other border controls.
Just as Europe's travel season is reaching its peak, officials started worrying about a second wave. Spain, in particular, has seen case numbers spike. France and Germany are now contending with their highest infection rates since April.
The changes reflect a sense that the attempt to reboot the Mediterranean's tourism economy has undercut Europe's fight to control the virus. Vacation-popular Greece and Croatia, which largely missed Europe's first wave, have seen a surge in cases in some of their most visited regions and are now dealing with their largest outbreaks to date.
Italy reports that 30 percent of its new cases come from people who were infected abroad. Germany puts its figure at nearly 40 percent. Austrian Chancellor Sebastian Kurz said that "the virus is coming to Austria by car."
European governments have agreed that it's okay to curtail free movement - a fundamental principle of the European Union - from places that have higher rates of transmission.
Newly imposed restrictions can be complicated to follow.
In some cases, they apply to everyone travelling.
In other cases, they are limited to certain high-risk areas. People travelling from Barcelona to Belgium, for example must observe a mandatory 14-day quarantine. For those who have been in Madrid, a quarantine is merely recommended.
In Germany, negative tests can get people out of having to self-isolate upon arrival. Some other countries offer no option but to hunker down for two weeks. Britain has been adding back to its list of European countries it advises against travelling to.
First, Spain, then Luxembourg, Malta and France. British media have speculated that Croatia could be next - a decision that would force an estimated 20 000 vacationers to either race home or be subject to quarantine. Croatia reported earlier this month that it was hosting more than 800 000 tourists, 70 percent of the total from a year ago.
"At the moment," said Walter Ricciardi, the World Health Organization's Italian government adviser, "the freedom of people to get around Europe should be limited according to the number of cases."