Travellers arriving in England from seven Greek islands will have to quarantine from 4 a.m. London time on Wednesday, UK transport secretary Grant Shapps has announced.

Holidaymakers travelling from Lesvos, Tinos, Serifos, Mykonos, Crete, Santorini and Zakynthos will have to self-isolate for 14 days after returning from the islands due to rising coronavirus cases.

“Data from the Joint Biosecurity Centre and Public Health England has indicated a significant risk to UK public health from those islands, leading to Ministers removing them from the current list of travel corridors,” the transport department said in a press release.

The announcement came as part of a new policy that allows the UK to add and remove islands from the UK’s quarantine exception list, Shapps said in the House of Commons. Mainland Greece will thus remain on England’s travel exemption list.

The UK first issued travel quarantines for many international countries and territories determined to be at risk for COVID-19, often with incidence rates higher than in the UK.