A series of Covid measures come into force today in Britain in an attempt to tackle the new Omicron variant.
People in England will have to wear face coverings in shops or on public transport.
And - along with Wales - they're also being advised for secondary school students.
Meanwhile all international arrivals must self-isolate until they get a negative PCR test result.
UK Health secretary, Sajid Javid, says he doesn't want to "jump to any conclusions" about this new strain.
"What we do know at the moment about the variant is that it is worrying, and that's why we've taken these swift responses.
"It's important that we take the time to assess it, take the time that's needed, hopefully in the next few weeks that can be done."
