Swiss health authorities have said they will impose a 10-day quarantine on travelers from Spain, except those arrving from the Canary and Balearic islands.
The measure will take effect this Saturday, and health authorities warned that self-isolation will be mandatory even with a negative Covid-19 test.
The Valencia region, Catalonia and Andalusia stand to lose the most from the decision.
Switzerland ranks 11th on the list of source countries for tourists visiting Spain.
Last year, 1.82 million Swiss citizens, out of a nation of 8.5 million people, came on holiday to Spain.
While statistics show that most Swiss visitors go to the Canary and Balearic islands, which are excluded from the quarantine rule, in August last year there were just over 40,000 Swiss visitors in the Valencia region, 27,000 in Catalonia and 25,000 in Andalusia.