London CNN  — 

The UK’s response to the coronavirus pandemic was upended on Friday when the Prime Minister Boris Johnson and his top health minister tested positive for the infection, and his chief medical adviser self-isolated after displaying symptoms.

Johnson announced his diagnosis in a remarkable video posted on social media, in which he said he would continue to lead the UK government’s efforts from self-isolation in an apartment in Downing Street. Minutes later, his secretary of state for health, Matt Hancock, also said he had the virus and would work from home.

The Prime Minister said he’d been tested on the advice of England’s chief medical officer, Chris Whitty. A matter of hours later, Whitty said he was going into self-isolation after displaying symptoms of Covid-19.

The extraordinary developments raised the question of how many officials leading the UK’s response to coronavirus had themselves been exposed to it. Downing Street, the center of power in the UK, is a maze of cramped offices and narrow corridors, making it almost impossible for everyone working there to practice the government’s own advice on social distancing.

On Thursday evening, after displaying symptoms but before learning the result of his test, Johnson appeared outside 10 Downing Street with his chief finance minister, Rishi Sunak, taking part in a national moment of appreciation for the UK’s health service workers. A Downing Street spokesperson said the pair were careful to remain at a safe distance.

Boris Johnson, right, taking part in a national applause with his chancellor, Rishi Sunak.

Johnson was a late convert to the strict measures now in place in the UK. Only a few weeks ago, he boasted of shaking the hands of coronavirus patients in hospital, and the UK faced criticism for a more cautious approach to the restrictive measures adopted by its European neighbors.

“Over the last 24 hours I have developed mild symptoms and tested positive for coronavirus,” Johnson said in his Friday Twitter post. “I am now self-isolating, but I will continue to lead the government’s response via video-conference as we fight this virus. Together we will beat this.”

In a video, Johnson said he was experiencing a temperature and a persistent cough, which are key symptoms of the virus. He added that he was working from home and self-isolating. “But be in no doubt that I can continue, thanks to the wizardry of modern technology, to communicate with all my top team to lead the national fightback against coronavirus,” he said.

Johnson will work in isolation from his four-bedroom apartment in Downing Street. The infection also raises concerns over Johnson’s fiancee, Carrie Symonds, who is pregnant, and the myriad of other officials and advisers who work in close quarters in Downing Street.

Whitty, who has appeared alongside Johnson at many of the daily press conferences held at Downing Street in the past two weeks, said he would spend the next week at home. “After experiencing symptoms compatible with COVID-19 last night, in line with the guidance, I will be self-isolating at home for the next seven days. I will be continuing to advise the Government on the medical response to Coronavirus, supported by my deputies,” Whitty wrote on his Twitter page.

The announcements come just over a week after a top government adviser on the virus, Neil Ferguson, said he believed he had been infected and warned: “There is a lot of Covid-19 in Westminster,” referring to the area of London that is home to the UK Parliament and other government premises.

Ferguson had met with the Prime Minister, as well as Whitty, and Chief Scientific Adviser Patrick Vallance. It was unclear, however, where Johnson may have contracted the virus.

Days earlier, the heir to the UK throne, Prince Charles, revealed that he had contracted the virus and was isolating himself at his estate in Scotland.

Johnson had been criticized for continuing to shake people’s hands in public while government advice was to keep around two meters away from other people. The Prime Minister, Whitty and Vallance have been giving regular in-person press conferences to journalists on the virus after meetings.

His government has also come under pressure to test for the virus more widely and to provide WHO standard protective gear for doctors and nurses across the country.

In the event that Johnson is unable to fulfill all his duties as prime minister, Foreign Secretary Dominic Raab would be expected to stand in his place. Raab previously served as Brexit Secretary under the government led by Theresa May. He stepped down after the UK and EU agreed on a draft Brexit deal, which he claimed had “fatal flaws.”

Johnson last met with Queen Elizabeth II on March 11, Buckingham Palace said Friday. “The Queen last saw the PM on the 11th March and is following all the appropriate advice with regards to her welfare,” the palace said in a statement.

British health authorities announced another 181 fatalities on Friday, bringing the death toll to 759. More than 14,500 infections have been recorded, but as the UK is not testing widely, true infection numbers are likely to be much higher.