Prime Minister Boris Johnson and Health Secretary Matt Hancock have tested positive for coronavirus, while the government's chief medical officer Chris Whitty is self-isolating with Covid-19 symptoms.
Cabinet minister Michael Gove, who stood in for the prime minister in the daily coronavirus press conference, said the diagnoses of his colleagues shows that the “virus does not discriminate”, adding: “We are all at risk.”
Prime Minister Johnson revealed his diagnosis on Twitter, as did the health secretary, with both posting videos explaining how they would continue to work through self-isolation.
Mr Johnson's video said he was experiencing "mild symptoms" but would "continue to lead the government’s response" to Covid-19 via video-conferencing.
He said "thanks to the wizardry of modern technology" he can carry on working and communicating with his "top team" to "lead the national fightback".
Mr Hancock, speaking to ITV News via Skype, said: "What really matters is that have we got the beds to treat people who have serious coronavirus complications".
He added: "That's what I've been working at so hard over the last few days both in the office and at home, pushing that is incredibly important."
Daily coronavirus press conference key points:
A further two UK facilities are being converted into temporary coronavirus hospitals
New 'NHS Nightingale' hospitals to be built in Birmingham’s National Exhibition Centre and Manchester’s Central Convention Centre “with further such hospitals to follow”
Testing of frontline NHS staff to determine whether they have or have had coronavirus will start next week, including critical care nurses, intensive care staff, ambulance workers and GPs
Government's coronavirus response team will only be tested if they have symptoms, despite PM's diagnosis
Data used by the Government to justify the stringent lockdown on the UK will soon be released
Hours later the government's chief medical officer revealed he was also self-isolating after suffering "symptoms compatible with COVID-19".
Chris Whitty says he will be "continuing to advise the Government on the medical response to Coronavirus".
In the press conference Mr Gove revealed how Government had brought together universities, businesses and research institutes in a “new alliance” to boost testing capacity for frontline workers.
“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.
“These tests will be trialled for people on the frontline starting immediately, with hundreds to take place by the end of the weekend – dramatically scaling up next week.”
It was also revealed how a further two UK facilities would be turned into temporary coronavirus hospitals, after the conversion London's Excel Centre began earlier this week.
NHS England's Chief Executive Simon Stevens, who also spoke at the press conference, said he had given the go ahead to building two further hospitals, one in Manchester's Central Convention Centre and one in Birmingham's NEC.
He said that will make available 33,000 hospital beds to treat coronavirus patients.
One issue that will be of concern for the prime minister is that because his fiance Carrie Symonds is pregnant, she falls into one of the more vulnerable groups.
ITV News Science Editor Tom Clarke on Boris Johnson testing positive for coronavirus
Pregnant women, along with those over 70 and people with health conditions were the first groups “strongly advised” to undertake social distancing measures.
Downing Street suggested that the PM’s pregnant fiancee Carrie Symonds is not living with Mr Johnson at present.
Asked about their living situation, the PM’s official spokesman said: “The Prime Minister of course follows all of the guidelines which have been issued by Public Health England in full.
“His circumstance is such that he will be required to self-isolate for seven days.”
The spokesman said meals and work would be left at the door of the Prime Minister’s flat, which is going to be inside 11 Downing Street during his period of isolation.
The spokesperson said Mr Johnson noticed that he had mild symptoms on Thursday afternoon and received the test results at midnight.
If Mr Johnson's symptoms worsen to the point he is unable work, it is believed Foreign Secretary Dominic Raab will step in as acting PM.
The Queen, who is 93 years old, last saw the prime minister was on March 11, one day before she last saw her son Prince Charles, who is also infected.
It is thought to be unlikely either were infectious when they met with the monarch, but the timings are close.
A Buckingham Palace spokesman confirmed the Queen last saw Mr Johnson just over two weeks ago.
He said: “Her Majesty the Queen remains in good health. The Queen last saw the Prime Minister on the 11th March and is following all the appropriate advice with regards to her welfare.”
The PM’s spokesman said Mr Johnson had been conducting his weekly audiences with the Queen by telephone for “at least the last fortnight”.
It is not known the last time Mr Johnson saw his 79-year-old father Stanley, who wished his son a speedy recovery.
He told ITV News: "Very sorry to hear it and we have sent a message to the PM sending our love and wishing him a very speedy recovery".
Support for the prime minister poured in from across the political spectrum, with many wishing him a full recovery.
Labour leader Jeremy Corbyn tweeted: “I wish the Prime Minister a speedy recovery and hope his family are safe and healthy.
"Coronavirus can and does affect anyone. Everyone be safe. Our own health depends on everybody else.”
Nigel Farage posted: “Wishing @BorisJohnson well and a very rapid recovery.”
And former chancellor Sajid Javid replied: “Get well soon. Sending you best wishes from Javid family and Bailey.”
She wrote on Twitter: "I don't wish anyone ill. I wish the Prime Minister a speedy recovery.
"I hope everyone in coming days gets the care and medical attention they need."
A Downing Street spokesperson said: “After experiencing mild symptoms yesterday, the Prime Minister was tested for coronavirus on the personal advice of England’s Chief Medical Officer, Professor Chris Whitty.
“The test was carried out in No 10 by NHS staff and the result of the test was positive.
“In keeping with the guidance, the Prime Minister is self-isolating in Downing Street.
“He is continuing to lead the government’s response to coronavirus.”
Mr Johnson is the latest in a series of world leaders to have been affected by the virus.
Canadian Prime Minister Justin Trudeau and German Chancellor Angela Merkel have both been forced to self-isolate after coming into contact with people infected with Covid-19.
Coronavirus: Everything you need to know: