Scotland, England and Northern Ireland have introduced tougher restrictions which in some instances will bring penalties for those breaching the measures.
A new Covid-19 lockdown has come into force on mainland Scotland. It's now illegal to leave home unless it's for an essential reason - like food shopping or caring responsibilities - and schools will remain shut.
The First Minister says she's more concerned about the rate of infection than she has been at any point of the pandemic.
Nicola Sturgeon's announced the measures will last for the whole of January - and maybe beyond that.
Further south, a third national lockdown has started in England with people being told to stay at home.
Boris Johnson has warned the new Covid-19 variant is spreading in a "frustrating and alarming" manner.
Anyone who was cocooning back in March, is again being asked to do so.
It also means schools are shut until the middle of next month
Meanwhile schools are to remain closed in Northern Ireland for the foreseeable future.
The Stormont Executive will meet today to finalise a tightening of the current six-week lockdown.
It will include an extended period of remote learning and new rules on travel.
First Minister Arlene Foster says stay-at-home laws will also be re-introduced, after being in place during the first wave.