ATHENS—Unvaccinated workers in restaurants and tourism companies on some of Greece’s main holiday islands will be regularly tested for COVID-19 after the Delta variant fuelled a surge in infections, a minister said on Thursday. Mykonos, Santorini, Ios, Paros, and the cities of Rethymnon and Heraklion on the island of Crete have all seen rapid increases in cases in recent days, Deputy Citizen’s Protection Minister Nikos Hardalias told a news conference. The workers, as well as crew on ferries and cruise ships, will have to be tested twice a week from Saturday onwards if they haven’t been vaccinated, he added. The government has been hoping for at least a partial revival of its crucial tourist industry over the summer, but has tightened restrictions as cases have spread. This week, the government said customers at indoor restaurants and bars would have to prove they had been vaccinated. Greece reported 2,794 new infections …