With the spread of the virus "doubling every three to four days” - as was revealed by stand-in Michael Gove at yesterday's coronavirus press conference - it's no surprise that Health Secretary Matt Hancock also has also contracted it.
One of their top coronavirus advisers has also been forced into self-isolation after also experiencing "mild symptoms", but like the PM and health secretary, Chief Medical Officer Chris Whitty will continue to work from home.
Mr Johnson, who is suffering with a "temperature and persistent cough", says thanks to the "wizardry of modern technology" he can continue to manage the response by communicating via video.
Mr Gove said the diagnoses of his colleagues shows that the “virus does not discriminate”, adding: “We are all at risk.”
On Saturday Scottish Secretary Alister Jack revealed he has developed mild symptoms associated with coronavirus and is self-isolating.
With 55-year-old Mr Johnson testing positive for the virus on Thursday evening, questions have been raised as to who else he may have infected.
It is believed his girlfriend Carrie Symonds, considered vulnerable due to her pregnancy, is safe after it was reported she moved out of Downing Street several days ago, before the PM was experiencing symptoms.
Mr Johnson's spokesman said he is living in the flat in 11 Downing Street, and with the chancellor moving out, the whole building will serve as his office and house - meals and work would be left at the door.
It is thought the Queen is also likely to have avoided being infected by the prime minister - a No 10 spokesman said Mr Johnson had been conducting his weekly audiences with Her Majesty by telephone for “at least the last fortnight”.
Concerns have been raised about which Cabinet minister will be stricken next, with Chancellor Rishi Sunak spending time with the PM as recently as Thursday evening and Home Secretary Priti Patel sitting close to him on Wednesday at PMQs.
But, as Chancellor of the Duchy of Lancaster Gove said in the daily press conference, ministers will only be tested if they're "symptomatic".
He also revealed how the government was ramping up its testing capabilities to ensure frontline staff, including critical care nurses, intensive care staff, ambulance workers and GPs, are able to be tested swiftly.
“This will be antigen testing – testing whether people currently have the disease – so that our health and social care workers can have security in the knowledge that they are safe to return to work if their test is negative."
He said trials of the tests will begin "immediately, with hundreds to take place by the end of the weekend – dramatically scaling up next week".
And following much speculation, the press conference also confirmed the creation of two new coronavirus field hospitals.
After work began converting London's Excel centre into a 4,000 bed 'NHS Nightingale Hospital', the Ministry of Defence will also convert Birmingham's NEC and Manchester's Central Convention Centre.
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NHS chief executive Sir Simon Stevens said building new hospitals in "very short order" was an "extraordinary action".
He said he had "given the go-ahead" to the additional hospitals because this problem is "not just confined to London" and he said there would be “further such hospitals to follow”.
However, while it appeared the government was making strides in the fight against the virus, new statistics showed that Friday had in the biggest daily rise of infections since the outbreak began.
A further 181 people in the UK died after contracting the coronavirus, bringing the death toll to 759.
The number of people to have tested positive for the virus rose by nearly 3000, bringing the number of confirmed cases in the UK to 14,579.
At the the daily press conference, Mr Gove declined to be drawn on whether MPs had been too slow in practising social distancing.
He instead said the diagnosis of Mr Johnson and Mr Hancock showed the “virus does not discriminate”, warning: “We are all at risk.”