LONDON: British Prime Minister Boris Johnson was moved to an intensive care unit on Monday (Apr 6) after his coronavirus symptoms worsened, although his Downing Street office said he was still conscious.
Britain has no formal succession plan should the prime minister become incapacitated, but Johnson, 55, has asked Foreign Secretary Dominic Raab to deputise for him.
Johnson was admitted to St Thomas' Hospital in central London late on Sunday after suffering persistent coronavirus symptoms, including a high temperature, for more than 10 days.
He is the most high-profile world leader infected with the disease that has spread rapidly across the globe.
His condition rapidly deteriorated over the next 24 hours, and he was moved to an intensive care unit - where the most serious cases are treated. Although he had received oxygen, his office said he was still conscious.
"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," said the Downing Street press release.
"The PM has asked Foreign Secretary Dominic Raab ... to deputise for him where necessary," it added.
Downing Street said the move to intensive care was "a precaution should he require ventilation to aid his recovery".
READ: UK Prime Minister Boris Johnson in hospital as 'precautionary step' 10 days after contracting COVID-19
"Doctors will be monitoring important vital signs such as oxygen saturations," said Rupert Beale, group leader at the cell biology of infection laboratory at the Francis Crick Institute.
He said they would also check Johnson's blood to "see what the immune response to the virus looks like, and to assess liver and kidney function", and may also perform an electrocardiogram to check the heart.
The British government has been criticised for initially refusing to follow other European countries in requiring people to stay home as the virus spread.
And Johnson himself said in early March that he was still shaking hands with people.
But two weeks ago he ordered a nationwide lockdown and Britain is now in the grip of a serious outbreak.
The official death toll in the United Kingdom, which has more than 50,000 cases, currently stands at 5,373, and last week the health minister said the deadliest peak for deaths was projected to be Easter Sunday, Apr 12.
Health Secretary Matt Hancock and the heir to the throne, Prince Charles, have both been infected with coronavirus, although they have since recovered.
In response to the crisis, Queen Elizabeth II made a rare public address on Sunday night, evoking the spirit of World War II and urging Britons to stay united.
"We will be with our friends again, we will be with our families again, we will meet again," she said.
Housing minister Robert Jenrick told BBC television that the prime minister had been working "phenomenally hard" during the crisis, adding that he would be finding it "very frustrating" to be ill.
Johnson is not known to have any underlying health issues, although he has struggled with his weight, but some questioned if he should have taken more time off. He plays tennis and while mayor of London used to cycle around the capital.
Junior health minister Nadine Dorries, who also had coronavirus but has recovered, added: "Many with #COVID19 are felled by fatigue/temperature and use isolation to sleep and recover.
"Boris has risked his health and worked every day on our behalf to lead the battle against this vile virus."
Sarah Vine, a newspaper columnist and wife of senior cabinet minister Michael Gove, added: "Boris has worked non-stop throughout his illness - and now we see the result."
US President Donald Trump said he was "hopeful and sure" Johnson would recover, calling the prime minister "a friend of mine" and a "great leader".
French President Emmanuel Macron said he hoped that Johnson would quickly overcome the "ordeal".
"My full support to Boris Johnson, his family and the British people at this difficult time. I hope he will rapidly overcome this ordeal," Macron tweeted.
Theresa May, Johnson's predecessor as prime minister, said: "My thoughts and prayers are with Boris Johnson and his family as he continues to receive treatment in hospital."
Johnson's pregnant partner, Carrie Symonds, moved out of Downing Street after some staff fell ill. But she said on Saturday she had just spent a week in bed with symptoms, although she has not been tested.
Stand-in leader Raab, 46, said the British government would continue to make sure Johnson's plans for defeating the coronavirus outbreak were carried out while he receives treatment.
"The government's business will continue," Raab told reporters.
"The prime minister is in safe hands ... and the focus of the government will continue to be on making sure that the prime minister's direction, all the plans for making sure that we can defeat coronavirus and can pull the country through this challenge, will be taken forward."
Raab, the son of a Czech-born Jewish refugee who fled the Nazis in 1938, was brought up in the southern English region of Buckinghamshire and studied law at Oxford University before becoming a lawyer working on project finance, international litigation and competition law.
A karate black belt, he was appointed as foreign minister in Johnson's first Cabinet after the prime minister took office in July 2019.
Asked at a news conference earlier on Monday whether he had been in touch with Johnson on Monday by either text or by telephone, Raab said he had last spoken to the prime minister on Saturday.