Germany's foreign ministry updated its travel advisory on Tuesday, recommending against travel to three regions in northern Spain grappling with renewed outbreaks.
“Non-essential tourist travel to the autonomous communities of Aragon, Catalonia and Navarra are currently discouraged due to renewed high levels of infections and local lockdowns,” a statement said.
“We must prevent that the virus once again spreads rapidly and uncontrollably,” Robert Koch Institute head Lothar Wieler told reporters.
The RKI chief said Germans bringing the virus back from their summer holidays was one reason for the surge in cases, but he also pointed to outbreaks happening at workplaces and open-air parties.
Germany's disease control agency voiced “great concern” over rising virus numbers in the country as authorities issued the travel warning against parts of Spain.
Spain's cumulative coronavirus rate has been growing in recent weeks, but with large regional disparities.
A spike in the infection rate in the northern regions of Catalonia (63.1 per 100,000 inhabitants), Aragón (160.1 per 100,000) and Navarre (79.2 per 100,000) have pushed Spain's average up to 39.4 per 100,000 inhabitants, far higher than Germany's infection rate of 7.7 (data from European Centre for Disease Prevention and Control).
The travel advice by the German government follows the UK's sudden decision on Saturday to impose a 14-day quarantine on British holidaymakers returning from Spain.
The Spanish government is fighting to save the country's tourism industry, arguing that other popular holiday hotspots such as the Canary Islands, the Balearic Islands, Andalusia and the Valencia region have a far lower rate of infections.
Germany has so far recorded a total of 206,242 coronavirus cases and 9,122 deaths.
Berlin has taken great pride in keeping the fatality numbers low, crediting its world-class health system and widespread early testing for the success.
But Wieler said other countries such as Israel had shown how quickly the situation can change.
Over the last seven days, Germany has registered an average of 557 new cases a day, up from around 350 in early June.
“We don't know yet if this is the beginning of a second wave but of course it could be,” Wieler said.
“But I am optimistic that if we follow the hygiene rules we can prevent it, it's up to us.”
Germany has fared better than many of its neighbours in suppressing the virus, but Wieler urged citizens not to squander the progress following a spike numbers in recent weeks.
“It's in our hands how the pandemic evolves in Germany,” Wieler said, calling on Germans to stick with prevention measures such as washing hands and keeping a safe distance.
Face masks should be worn not only indoors, but also outdoors, if the recommended 1.5-metre (5-foot) distancing cannot be maintained, he said, in a subtle update of the prior advice.
The stark warning comes as countries around the world grapple with a surge in infections, fuelling fears of a dreaded second wave.