Prime Minister Boris Johnson tested negative for Covid-19 on leaving hospital, his official spokesman said.
The spokesman said it was “standard practice” to be tested before leaving hospital.
Mr Johnson was discharged from St Thomas’ Hospital on Sunday after a week’s stay, including three nights in intensive care.
He is recovering at his country residence, Chequers, and has been reunited with his pregnant fiancée Carrie Symonds.
His spokesman added he is not “currently carrying out government work” and is “focusing on his recovery.”
Pressed on how ill the PM was, Mr Johnson’s spokesman said: “As we set out, his condition did worsen over the course of last Monday afternoon and he had to be moved to the intensive care unit.
“Now, clearly, if a person is moved to intensive care, that means that they are requiring a significant level of specialist treatment.
“So, I think it was clear from the moment the Prime Minister was moved to intensive care that his condition had worsened.”
Mr Johnson hailed the medics who looked after him at St Thomas’ and said without question the NHS had saved his life.
In an emotional speech posted on social media following his hospital release, the prime minister it “could have gone either way” and praised two nurses who stayed by his side for 48 hours.
One of the nurses – Jenny McGee - said it was a "surreal time", as she couldn't believe "she was actually treating the prime minister of the UK".
Mr Johnson called the NHS “unconquerable” after seeing first-hand how it was dealing with the pandemic.
He said: “We will win because our NHS is the beating heart of this country.
“It is the best of this country. It is unconquerable. It is powered by love.”
The prime minister was initially admitted to hospital with persistent coronavirus symptoms last Sunday, but moved to the intensive care unit when his condition worsened.
He was discharged back to a ward on Thursday and was said to have been in “extremely good spirits”.
The PM’s spokesman said Foreign Secretary and First Secretary of State Dominic Raab will speak at the daily government press conference on Monday.
"He spoke to the First Secretary of State over the course of the weekend,” the spokesman added.
"The Prime Minister is focusing on his recovery and he is not currently carrying out Government work."
Mr Raab will continue to stand in for Mr Johnson during a week in which the government is due to face key decisions over the future of the lockdown.
The formal review of the strict social distancing measures is due, as per the emergency powers legislation, to be reviewed by ministers on Thursday.
Downing Street said it would only look to lift restrictions once science and medical advisers recommended doing so.
But there is thought to be economic pressure to consider, with both the Telegraph and the Times reporting that Chancellor Rishi Sunak is set to unveil modelling to Cabinet colleagues about the impact that extending the lockdown could have.
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