"THE BAD MOMENT"
Johnson's sudden deterioration after continuing to work may hold a warning for the 74-year-old Trump, now in full campaigning mode for the U.S. presidential election on Nov. 3.
Johnson was admitted to St Thomas’ Hospital in the evening of April 5. The next day he was moved to intensive care, where he received oxygen support but was not put on a ventilator.
"The bad moment came when it was 50-50 whether they were going to have to put a tube down my windpipe," Johnson said later.
"The doctors had all sorts of arrangements for what to do if things went badly wrong ... The bloody indicators kept going in the wrong direction."
He later said he owed those doctors his life.
While Johnson was ill, his duties were assumed by Foreign Secretary Dominic Raab.
"They had a strategy to deal with a 'death of Stalin'-type scenario," Johnson later said. "It was a tough old moment, I won’t deny it."
Johnson left hospital on April 12, but continued his recuperation at his official country residence northwest of London, and did not return to work until April 27 - a month after announcing that he had tested positive.
When Johnson's fiancée Carrie Symonds gave birth to their son two days later, he was given a middle name of Nicholas partly in tribute to two of the intensive care doctors who had treated the prime minister.
Since then, Johnson has repeatedly dismissed concerns about his recovery, and said the virus has convinced him to slim down from his previous, portly 17st 6lb (244 lb, 112 kg).
As recently as Tuesday, he told a reporter: "I'm fitter than I was before, it may irritate you to know ... I'm fit as a butcher's dog, thanks basically to losing weight."