Travellers arriving home to Wales from Zante are being asked to self-isolate for 14 days.
Wales’ Health Minister Vaughan Gething said there are six clusters of cases, amounting to 30 infections, from flights from the Greek island.
All passengers arriving on a flight from Zante to Cardiff on Tuesday night will be offered two Covid tests – one in 48 hours and another in eight days.
Mr Gething said the passengers posed a public health risk.
It comes after at least 16 people tested positive following a flight from the Greek island last week.
Passengers on the 22:40 BST arrival from Zante, operated by TUI Airways, will be given a letter asking them to self-isolate.
Travellers arriving from other UK airports from the island on Tuesday and Wednesday are also being asked to seek tests when they arrive home, and again in eight days.