At least 55 people in the UK have died after contracting coronavirus, the health secretary has revealed, a jump of 19 from 36 on Sunday.
Matt Hancock said the spread of the disease is now "accelerating" and it is the "most serious public health emergency that our nation has faced for a generation".
Some 1,543 people in the UK have now tested positive for the virus - an increase of 171 cases from the same point on Sunday.
The news came after Boris Johnson said the UK was taking "drastic action" to deal with the virus.
He said he was asking for increased social distancing to stem the "fast growth" of coronavirus across the UK.
He said "people in the UK should avoid pubs, clubs and theatres, stop all non-essential contact and travel, and work from home if they can".
It comes after Wales' Chief Medical Officer confirmed the death of the first coronavirus patient in Wales.
The 68-year-old - who had underlying health conditions - died at the Wrexham Maelor Hospital.
In Scotland, the number of confirmed Covid-19 cases rose to 171 - an increase of 18 from the same time the day before. While Northern Ireland recorded seven new cases since Sunday, Stormont health minister Robin Swann confirmed.
Health officials said a total of 44,105 people have been tested for the virus across the UK.
On Monday Boris Johnson held the first of daily press conferences being planned to update the public on Covid-19.
It followed an emergency meeting of the Cobra committee on Monday afternoon to discuss the Government's approach to the outbreak.
Mr Johnson urged the public to work from home when possible and to avoid pubs, clubs and theatre and said that anyone who lives with someone who has a cough or a temperature should stay at home for 14 days and not even venture out for supplies if possible.
According to the Scientific Advisory Group for Emergencies (Sage), he said, "it looks as though we are now approaching the fast growth part of the upward curve" in the number of cases.
"Without drastic action cases could double every five or six days," the PM warned.
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Schools were issued new guidance on Monday, with educators told they should send home pupils who have a continuous cough or fever as a way help mitigate the impacts of the virus.
But updated information from the Government says all educational settings should remain open unless directly advised to close by Public Health England (PHE).
On Sunday, Health Secretary Matt Hancock said over-70s could be told to stay home for up to four months within the "coming weeks".
Under the Health Protection (Coronavirus) Regulations 2020, which were passed last month, a person who is required to be kept in isolation can be taken there by a constable, with the use of "reasonable force, if necessary".
Failure to comply with restrictions, or absconding from isolation, is punishable with a fine of up to £1,000.