People should avoid unnecessary contact and stick to lockdown rules, England's chief medical officer Prof Chris Whitty has said. The surge in coronavirus cases "is everybody's problem", he argued.
England, Northern Ireland, Scotland and Wales have all introduced lockdowns.
What are England's lockdown rules?
People in England must stay at home and only go out for certain reasons.
It is illegal to leave home without a "reasonable excuse". If you don't have one, police can fine you £200 for a first offence - doubling for further offences up to a maximum of £6,400.
You are not allowed to leave home to meet people socially if you don't live together, or have a support bubble with them.
What's a "reasonable excuse" for leaving home?
- Shopping for essentials such as food and medicine
- Meeting your support or childcare bubble
- Children can move between separated parents
- Working or volunteering where it is "unreasonable" to work from home. This includes work in someone else's home - for example nannies, cleaners and tradespeople
- Education, training, childcare, medical appointments and emergencies
- Religious worship
- Moving house
Exercise outdoors once a day is also a "reasonable excuse" for leaving home.
You can exercise with other person from another household in an open public space. You should stay two metres apart from each other.
If you do leave home for one of these reasons, you should stay local - unless it is necessary to go further, for example to go to work.
"Stay local means remaining in the village, town, or part of the city where you live," government guidance says.
Travel - internationally or around the UK - is only allowed if it is essential.
If you are clinically extremely vulnerable you should only go out for medical appointments, exercise or if it is essential. You should not attend work.
Hospitality businesses such as pubs and restaurants and non-essential shops have closed, as have indoor and outdoor sports facilities including gyms and tennis courts.
Essential businesses and services can stay open - including:
- Supermarkets, food shops, pharmacies and garden centres
- Places of worship
- Petrol stations and MOT services
- Banks and post offices
- Doctors and dentists' surgeries and vets
- Car parks, public toilets and playgrounds
What are the restrictions in Scotland?
Scotland has its own restriction levels - from zero to four.
Mainland Scotland (and the isles of Skye, Arran, Bute and Gigha) have moved to "enhanced level four" until at least the end of January.
Orkney, Shetland, the Western Isles and other island communities remain in level three.
On 13 January, the Scottish Government announced six new rules that will come into force on Saturday.
"Enhanced" level four rules
- Nursery, primary and secondary schools close to all but vulnerable pupils and the children of key workers until February - learning moves online
- People should only leave home for essential reasons such as caring responsibilities, essential shopping, exercise or seeing their extended household
- Those who are shielding should not go into work, even if they cannot work from home
- A maximum of two people from up to two households can meet outdoors (under-11s are not included in the limit and can play together outside)
- Places of worship are closed except for weddings (up to five people) and funeral services (up to 20 people) - wakes are not allowed.
- The definition of an essential business has tightened with premises such as ski centres, large retail showrooms and cosmetic clinics required to close
- People should not travel outside their own local authority area for anything other than "essential" reasons
- It is illegal to travel between Scotland and other parts of the UK unless the journey is essential
- From Saturday 16 January, only shops selling essential items - such as clothing, footwear and baby equipment - will be allowed to offer click and collect
- From that date also, customers will not be allowed to collect takeaways from inside restaurants and it will no longer be legal to drink alcohol outdoors in public
Level three (very high) rules
- Pubs and restaurants can open until 18:00, but alcohol can't be served
- Leisure and entertainment venues must close
- Non-essential travel in or out of the area is not allowed
- Indoor gym use is restricted to individuals
- Hairdressers and barbers can open
Levels two, one and zero
None of these levels currently apply to any area in Scotland.
What are Northern Ireland's rules?
The new rules include:
- Closure of all non-essential shops, including garden centres and homeware stores
- No click-and-collect services, apart from supermarkets
- Closure of hair and beauty salons
- Hospitality businesses open only for takeaway and delivery
- Leisure and entertainment venues must close
- Off-licences must close by 20:00
- Weddings, civil partnership ceremonies and funerals limited to 25 people - wedding receptions not allowed
- Churches can open for communal service (this is under review)
- Elite sport allowed behind closed doors
What are the rules in Wales?
Wales is in a national lockdown at alert level four.
- You must stay at home, except for very limited purposes
- You must not visit other households, or meet other people you do not live with, unless they are in your support bubble
- Wedding receptions and wakes are not allowed
You should also:
- Work from home if you can
- Not travel without reasonable excuse
The following must close:
- Entertainment venues including theatres and concert halls
- Indoor and outdoor visitor attractions
- Sport, leisure and fitness facilities
- Pubs, bars and cafes (except for takeaway and delivery)
- Hairdressers and nail salons
- Non-essential shops (click and collect allowed)
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