The prime minister returned to work on Monday after convalescing for two weeks at Chequers, his country residence, with his pregnant fiancée Carrie Symonds following his discharge from hospital on Easter Sunday.
The 55-year-old spent three nights in intensive care after he was admitted on 5 April to St Thomas’ Hospital in central London, and later revealed his struggle with COVID-19 “could have gone either way” during that period.
Speaking outside 10 Downing Street, Johnson said the country is at maximum risk in the coronavirus outbreak, and urged people not to lose patience with the nationwide lockdown.
He said that although the UK was on its way to tackling the virus after social distancing measures ensured the NHS had not been overwhelmed during the peak of the infections, it was too early to ease the restrictions as doing so could risk a second wave of infections.
Johnson apologised for being "away from my desk for much longer than I would've liked" and thanked his colleagues who stood in for him, as well as the public and the NHS.
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He said: “If this virus were a physical assailant, an unexpected and invisible mugger – which I can tell you from personal experience it is – then this is the moment when we have begun together to wrestle it to the floor.
"And so it follows that this is the moment of opportunity, this is the moment when we can press home our advantage, it is also the moment of maximum risk.
"I know there will be many people looking at our apparent success, and beginning to wonder whether now is the time to go easy on those social distancing measures."
He said he understood concerns from business owners who were impatient to end the lockdown, but that this could lead to a second spike in cases and “cause more deaths, economic disaster and restrictions being reintroduced”.
"I ask you to contain your impatience,” he said, adding that there were "real signs now that we are passing through the peak".
While at Chequers last week, Johnson was in regular talks with those leading the UK coronavirus response, including foreign secretary Dominic Raab, who was deputising for him. This week will see him leading the government in public once again.
Health Secretary Matt Hancock, another leading figure in the battle against COVID-19, responded to Mr Johnson’s public appearance, tweeting: “Great to see the boss back and on top form.”
Nadine Dorries, the first minister to be diagnosed with the virus, said the PM was back to work quicker than many others would be in his situation.
“Most who have been as poorly as Boris Johnson with COVID-19 and a patient for a week in intensive care would be off work for at least three months to fully recover their strength and repair their immune system,” the health minister tweeted.
“Our PM is back after just three weeks. Good luck boss.”
Edward Argar, a health minister, said he was “hugely pleased” to see Johnson “back at work today with his health fully restored”.
He told BBC Radio 4’s Today programme the PM would be “looking very carefully” at how to lift the lockdown measures now that he was back at the helm.
In his speech outside Number 10, Johnson promised “transparency” over future decisions on social distancing and vowed to involve businesses and opposition parties when deciding a way forward.
More than 20,000 people who have tested positive for COVID-19 have died in hospitals, but the true death toll from the disease is much higher as this figures does not include deaths in care homes and the community.
Although Johnson said he was pleased with the government’s handling of the crisis in his absence, there has been criticism over a lack of personal protective equipment (PPE) for frontline staff and inadequate testing.
Lack of PPE has led to shortfalls on the NHS frontline, and supply problems throughout England have hampered delivery efforts.
Staff have reported being “terrified” over a lack of protective kit as they fear for the safety of themselves and their families.