The prime minister’s official spokesman confirmed he had been receiving “standard oxygen treatment” but had not required a ventilator at this stage.
Downing Street also confirmed he was not being treated for pneumonia.
Mr Johnson was transferred to the intensive care unit at St Thomas’ Hospital, London, yesterday evening, after his condition deteriorated.
His spokesman said the move was a “precautionary step” in case he needed to be put on a ventilator.
“The prime minister has been stable overnight and remains in good spirits,” the spokesman said. “He is receiving standard oxygen treatment and breathing without any other assistance.
“He has not required mechanical ventilation or non-invasive respiratory support.”
Mr Johnson was originally admitted to St Thomas’ on Sunday on the advice of his doctor after continuing to display symptoms of cough and high temperature 10 days after testing positive for the virus.
Mr Johnson’s fiancée Carrie Symonds is expecting a baby and also has symptoms of the virus.
Foreign secretary Dominic Raab has taken temporary control of the government while Mr Johnson is in hospital.
Weekly calls between Number 10 and the Queen will not take place while the PM is receiving treatment in intensive care, Downing Street added.
Article by Northern Gazette