He added: "I was not in particularly brilliant shape, and I was aware there were contingency plans in place".
Johnson, who was in hospital for a week being treating for Covid-19, thanked the National Health Service and its staff - but singled out two nurses who stood by his bedside for 48 hours "when things could have gone either way".
"Reality struck me when I was wired up to monitors and moved into intensive care".
T he interview follows an emotional video made by Johnson after being released from the hospital on April 12. I couldn't understand why I wasn't feeling any better.
After Johnson was discharged, St Thomas' said it was glad to have cared for the prime minister, but the hospital has given no details about the gravity of his illness beyond stating that he was treated in intensive care.
The doctors Boris Johnson named his son after are experts in infectious diseases and ventilation.
"They were starting to think about how to handle it presentationally", he said.
"It was thanks to some wonderful, wonderful nursing that I made it", he said to the Sun.
He also said he did not want to go to hospital at first but doctors were adamant because of his low oxygen levels.
On 30 April, Boris Johnson vowed to reveal his "comprehensive plan" for easing the lockdown next week, after declaring the United Kingdom has passed the peak of the coronavirus epidemic.
This plan is supposed to give a roadmap for easing the strict rules that were imposed in the country after a huge outbreak of coronavirus two months ago.
"The app will be important now after 4 May when we will reduce the gathering ban and the restrictions so we are prepared that the pandemic might rise again a little", said Aevar Palmi Palmason, head of the contact tracing team.
Testing for coronavirus is now widely available across Australia.
Meanwhile, the Communities Secretary said the Government was "optimistic" people will download a phone app to trace the spread of coronavirus.
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