Prime Minister Boris Johnson is “in good spirits” after spending the night in intensive care being treated for coronavirus, No 10 has said.
Mr Johnson, 55, was stable overnight, is being given oxygen and is not on a ventilator, a spokesman added.
The Queen has sent a message to Mr Johnson’s family and pregnant partner, saying they are in her thoughts.
It comes as Cabinet Office minister Michael Gove became the latest politician to self-isolate.
Mr Gove said he did not have symptoms but a family member did. He is continuing to work at home.
As of 17:00 on 6 April, of those hospitalised in the UK who tested positive for coronavirus, 6,159 have died – a record increase of 786 in a day, the Department of Health and Social Care said, compared with 439 on Monday.
Mr Johnson was admitted to St Thomas’ Hospital in central London with “persistent symptoms” of Coid-19 on Sunday and was moved to intensive care on Monday at 19:00 BST after his symptoms worsened.
Buckingham Palace said the Queen had sent a message to Mr Johnson’s family and his partner, Carrie Symonds, saying she was thinking of them, and wished the PM a full and speedy recovery.
Prince William also tweeted a personal message of sympathy to the PM’s family, signing it off with his initial “W”, while his father, the Prince of Wales, sent a message from himself and the Duchess of Cornwall wishing Mr Johnson a “speedy recovery”, Clarence House said.
In a statement on Tuesday, a Downing Street spokesman said: “The prime minister has been stable overnight and remains in good spirits. He is receiving standard oxygen treatment and is breathing without any other assistance.
“He has not required mechanical ventilation or non-invasive respiratory support.”
A ventilator takes over the body’s breathing process when disease has caused the lungs to fail.
Mr Johnson does not have pneumonia, Downing Street added.
Dr Jon Bennett, president of the British Thoracic Society, said it was “heartening” the PM was receiving “standard oxygen treatment” – through his nose or via a face mask – because in more serious cases it would be delivered through mechanical support, such as continuous positive airway pressure, high flow nasal oxygen or more invasive ventilators.
The spokesman said that the mood in government is “determined”, and ministers have a very clear plan set out by Mr Johnson for responding to the pandemic.
The prime minister’s weekly audience with the Queen will not go ahead, although she will be kept regularly informed about his condition, the spokesman added.
Speaking to BBC Radio 4’s Today programme, Mr Gove pledged that if there is any change in his condition “No 10 will ensure the country is updated”.
