The statement said, "This is a precautionary step, as the corona virus symptoms persist over the 10 days since the Prime Minister was found to be carrying the virus".
Number 10 Downing Street said he still remains in charge of the government.
"Stay healthy, Boris Johnson!". In a video posted to Twitter, he described his symptoms as "mild" at the time, which included fever and a persistent cough, and he has remained in isolation at an apartment on Downing Street since.
Johnson sent out a tweet thanking the National Health Service for taking care of him and others in this hard time. His pregnant partner, Carrie Symonds, said she has been ill with symptoms for a week but was now recovering. "He's a great friend of mine, a great gentleman and a great leader".
Johnson ordered a national lockdown on March 23 and has been shut away in his Downing Street apartment, in accordance with his own government's guidelines.
In a White House press briefing, U.S. president Donald Trump said he was sending "our nation's well wishes" for Johnson's "own personal fight with the virus". "Our thoughts and prayers are with him & we wish him a refuah shelaima umehaira - a full and speedy recovery".
Sir Stelios Haji-Ioannou also called on the company to oust its chief finance officer, Andrew Findlay, as he demanded the firm cancel its multi-billion pound contract with Airbus. "I'm shaking hands continuously", he'd said.
Under a section headlined "What to do if you need medical help while self-isolating", it says: "If you need medical help for any reason, do not go to places like a GP (family doctor) surgery, pharmacy or hospital".
US President Donald Trump said the US government had ordered 29 million doses of hydroxychloroquine, a drug used to treat malaria for which testing for its use to treat coronavirus is still under way.
The worsening news attracted loads of support with everyone from MPs to world leaders sending the prime minister their best wishes.