But he tweeted: “Following medical advice, I was advised to test for coronavirus. I’ve tested positive.
“Thankfully my symptoms are mild and I’m working from home & self-isolating. Vital we follow the advice to protect our NHS & save lives.”
The diagnosis will raise fears about how far into the heart of government infections have spread, with concern over the chief medical officer and chief scientific adviser.
The cabinet met around the famous Downing Street table as recently as last week – and some ministers were in the room with Mr Johnson this week.
The twin diagnoses are certain to raise questions about whether senior ministers, under the stress of an unprecedented crisis, have been maintaining social distancing rule adequately.
Following his symptoms, the prime minister dialled into the daily ‘war cabinet’ meeting from No 11 – where he lives – and will continue to do so while he is self-isolating.
“He will do the same things but that will be done exclusively via teleconferencing on his part,” his spokesman said.
Meals and work will be left outside Mr Johnson’s flat, while the doors between No 10 and No 11 have been closed off to all other staff who work in the building.
A spokesman for Rishi Sunak said the chancellor has not had any symptoms and therefore has not been tested for coronavirus and is not self-isolating.
As the health secretary’s infection was revealed, Dominic Cummings, the controversial No 10 chief aide, was seen running out of the door and to a nearby car.
Mr Hancock also issued a “massive thank you to everybody in the NHS, working in social care and right across the board on the response”.
“I’ll be continuing to do everything I can to get our carers the support that they need. And I’ll be doing that from here but with no less gusto,” he said, from his home.
“And then, from next Thursday, once I’m out of self-isolation and I hope with no more symptoms, then I’ll be able to get back stuck in and into the office where necessary.
“But the truth is that all of us can learn that working from home can be really, really effective.”
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