LONDON- British Prime Minister, Boris Johnson, has been moved to the intensive care unit of a London Hospital after being hospitalized Sunday for persistent coronavirus symptoms. 

"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 a spokesman.

"The PM has asked Foreign Secretary Dominic Raab, who is the First Secretary of State, to deputize for him where necessary," he added.

Downing Street has previously said Raab would stand in if the Prime Minister were unable to lead the country.

Last night, on the advice of my doctor, I went into hospital for some routine tests as I’m still experiencing coronavirus symptoms. I’m in good spirits and keeping in touch with my team, as we work together to fight this virus and keep everyone safe.

— Boris Johnson #StayHomeSaveLives (@BorisJohnson) April 6, 2020

Johnson's spokesperson said Monday that the PM had a comfortable night at St. Thomas' Hospital and is in "good spirits." Officials are no longer describing his symptoms as mild.

The Prime Minister was admitted to St. Thomas’ Hospital late Sunday, 10 days after he was diagnosed with COVID-19, the first major world leader to be confirmed to have the virus.

Downing Street said Johnson was conscious and did not require ventilation, but he was moved into intensive care in case he needs it later, his office said in a statement.

Hours earlier, Johnson tweeted that he was in good spirits and thanked the National Health Service for taking care of him and others with the disease.

“On the advice of my doctor, I went into the hospital for some routine tests as I’m still experiencing coronavirus symptoms,″ Johnson said in the tweet. “I’m in good spirits and keeping in touch with my team, as we work together to fight this virus and keep everyone safe.″