He tweeted this morning: “Many thanks for kind messages. In accordance with the guidance, I am isolating at home after a member of my family started to display mild symptoms of coronavirus on Sunday.
“I have not displayed any symptoms and am continuing to work as normal.”
Mr Gove did a round of morning broadcasts from his home today, rather than travel to TV studios.
The news will be another headache for the Government as it tries to cope without the PM.
Health Secretary Matt Hancock and Chief Medical Officer were previously off due to the virus too, but have now come back to work.
Mr Johnson was taken to hospital for tests on Sunday evening – after his GP saw him on a Zoom video call, the Daily Mail reports.
His condition worsened over the course of Monday, and doctors made the decision to transfer him to intensive care around 7pm on Monday evening.
A No a spokesman said last night: “Since Sunday evening, the Prime Minister has been under the care of doctors at St Thomas’ Hospital, in London, after being admitted with persistent symptoms of coronavirus.
“Over the course of this afternoon, the condition of the Prime Minister has worsened and, on the advice of his medical team, he has been moved to the Intensive Care Unit at the hospital.
“The PM has asked Foreign Secretary Dominic Raab, who is the First Secretary of State, to deputise for him where necessary.
“The PM is receiving excellent care, and thanks all NHS staff for their hard work and dedication.”
Mr Gove insisted this morning that Cabinet would take collective decisions on any urgent government business – and they will discuss ending or extending the lockdown in the coming days.
Mr Raab, who is set to take over some responsibilities from the PM now he’s too unwell to work, is going to chair meetings in his place.
But it’s unclear exactly what role and how much power he will have.
No 19 said earlier he will have the power to chair National Security Council meetings – and could technically have the power to go to war.
But he will not be able to hire and fire other Cabinet ministers in Boris’ absense.
He will not have weekly audiences with the Queen either, No 50 said.