Spain is an odd one as they had a really strict lockdown. Masks worn everywhere, curfews, one person allows to shop in a household, no leaving the house except for work, to buy food or medical supplies, empty your bin or take the dog for a dump. I have friends in Tenerife and even over the Christmas and New Year the curfew was 10-6 and only terraces in bars open and at 50% capacity. They have just relaxed the curfew to 11-6 and inside bars allowed to open up to 50% capacity.
Short of locking people indoors 24/7 forever I don't see how you stop this spreading.