Britain's Boris Johnson in hospital overnight with persistent coronavirus symptoms

UK Prime Minister tested positive for virus last month

British Prime Minister Boris Johnson has remained in hospital overnight with persistent coronavirus symptoms, the first world leader to be taken to hospital for the disease.

Tweeting from hospital, where Downing Street said the British leader was under observation, Mr Johnson said praised the work of National Health Service staff who had looked after him.

"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," he said.

General view of the empty Piccadilly Circus in London, Britain. EPA

View of an empty underground staircase at Piccadilly Circus in London, Britain. EPA

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A journalist is seen outside of the St Thomas' Hospital after British Prime Minister Boris Johnson was moved to intensive care after his coronavirus (COVID-19) symptoms worsened and has asked Foreign Secretary Dominic Raab to deputise. London, Britain. REUTERS

General view of 10 Downing Street after British Prime Minister Boris Johnson was taken into the intensive care unit in hospital on Monday evening, after his coronavirus (COVID-19) symptoms worsened and he has asked Britain's Secretary of State for Foreign Affairs Dominic Raab to deputise, in London, Britain. REUTERS

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A closed down traditional fish and chips van parked by the river Thames in London, Britain. EPA

A bus driver wearing a face mask is seen, as the spread of the coronavirus disease (COVID-19) continues, London, Britain. REUTERS

Rylan (12) playing football with his uncle Aaron, as the spread of the coronavirus disease (COVID-19) continues, Belfast, Northern Ireland. REUTERS

"I'd like to say thank you to all the brilliant NHS staff taking care of me and others in this difficult time. You are the best of Britain. Stay safe everyone, and please remember to stay at home to protect the NHS and save lives," the prime minister added.

Initially government officials said Mr Johnson was admitted to a London hospital as a "precautionary measure", adding that he remained in charge of the government.

Mr Johnson had been suffering from persistent symptoms, including a high temperature for days. His admission was not an emergency.

Foreign Secretary Dominic Raab is expected to chaired the government's coronavirus meeting on Monday morning in the prime minister's absence.

Mr Johnson was last seen in public applauding the NHS and other key workers from his flat in Downing Street on Thursday.

Speaking to the BBC, Housing and Communities Secretary Robert Jenrick said Mr Johnson was "still very much in charge of the government".

"He spent the night in hospital and of course we all wish him well and we hope that as a result of these tests he will be able to come back to Downing Street as soon as possible," Mr Jenrick said.

"I hope, I think we all do, that he has a speedy recovery and that he gets back to Number 10 and takes charge in the way he would want to as soon as possible," he added.

Despite the government's insistence the prime minister continues to lead the UK's Covid-19 response from hospital, there are increasing calls for him to rest and recover.

Conservative MPs have tweeted their support for the prime minister but have also said he should take this time to rest.

In the British press, senior government have officials have expressed their hope that Mr Johnson's hospital admission will act as a wake up call and he will cut back on his current punishing schedule.

The Department of Health said the number of coronavirus deaths in the UK stood at 4,934 as of 5pm on Saturday, an increase of 621 people from the previous day.

That same day, Mr Johnson's pregnant fiancee, Carrie Symonds, said she had also experienced coronavirus symptoms.

Westminster colleagues were quick to offer their support to Mr Johnson.

"Wishing our Prime Minister Boris Johnson every good health and a speedy recovery," Home Secretary Priti Patel said on Twitter. "We are thinking of you. Get well soon Boris."

Former leader of the opposition Labour party Jeremy Corbyn sent his best wishes to Mr Johnson and wished him a speedy recovery.

Mr Johnson has already had a coronavirus test which returned positive. It is unclear what tests he will receive in hospital but typically more acute Covid-19 patients receive lung imaging scans to check for pneumonia and well as blood tests. These tests will be used to determine whether or not the prime minister has entered the second stage of the disease where the immune system mounts a more aggressive response.

On Sunday evening, Britain's Queen Elizabeth II reassured the public that "better days will return", where people will be able to reunite with friends and family after the coronavirus pandemic.