The UK now has 2,626 confirmed cases of coronavirus after 676 more patients were diagnosed with the potentially deadly illness in the biggest day-on-day increase so far.
At least 72 people have died.
Scotland announced its third death on Wednesday, and the Department of Health is expected to announce the UK's updated death toll later.
The number of infected people is likely far higher, with health experts estimating about 55,000 people could be carrying the disease amid pledges to carry out more widespread testing.
The latest infection total was announced after Scotland and Wales said they were closing all schools from Friday.
England and Northern Ireland have not announced any closures, but it may come later.
The number of people to test positive for coronavirus in the UK as of 9am on Wednesday was 2,626, up from 1,950 at the same time on Monday, the Department of Health said.
It said on its website: "As of 9am on 18 March 2020, 56,221 people have been tested in the UK, of which 53,595 were confirmed negative and 2,626 were confirmed positive."
Britons in Spain have been urged by the Foreign Office to return before March 24 when all Spanish hotels close.
In a statement, it said: "The Spanish government have confirmed that all hotels will close in Spain from Tuesday 24 March.
"We therefore advise British travellers in Spain to contact their tour operator or airline as soon as possible, to arrange their return journey home before this date."
The coronavirus pandemic has killed more than 8,000 people worldwide.
More than 82,000 people have recovered so far, mostly in China.
In Scotland, the tragic third death came this afternoon as 32 new cases of coronavirus have been confirmed in Scotland.
The new cases this afternoon takes the total number to 227.
