The latest “big change” in coronavirus infections across the UK is of “great concern”, England’s deputy chief medical officer has warned.
Prof Jonathan Van Tam said people have “relaxed too much” over the summer and “we have got to start taking this very seriously again”.
If not, the UK will have “a bumpy ride over the next few months”, he warned.
He said that infections among younger people in EU countries had later filtered through to older age groups.
His comments came as more parts of the UK are to face tougher restrictions following a rise in the number of cases.
On Sunday UK authorities announced 2,988 new cases – the highest figure since 22 May, while a further 2,948 cases were reported in the 24 hours to 09:00 BST on Monday.
Stricter rules on home visits will be extended to two more areas in the west of Scotland from midnight.
In Wales, the county borough of Caerphilly is to be placed under a local lockdown from 18:00 BST on Tuesday.
And travellers arriving in England from seven Greek islands will have to self-isolate for 14 days from 04:00 BST on Wednesday.
They are Crete, Lesvos, Mykonos, Santorini, Serifos, Tinos, and Zakynthos (also known as Zante).