The monarch tested positive for Covid in February and, despite having what Buckingham Palace said were "mild cold-like symptoms", was determined to carry out what duties she could.
She later overcame her bout of the virus and described the experience during a virtual visit to the Royal London Hospital on Wednesday, to mark the official opening of the medical institution's Queen Elizabeth Unit.
During her video call with workers and medical staff, the Queen listened to their stories of coping with the huge influx of Covid patients, and was told by one senior nurse "we held their hands, we wiped their tears and we provided comfort".
Around 800 people from across north-east London were treated at the 155-bed Queen Elizabeth Unit, built in five weeks to meet the demand instead of the normal time period of five months, and the Queen hailed the Dunkirk spirit that inspired the construction team.
Speaking to former Covid patient Asef Hussain, and his wife Shamina, the Queen said about the virus: "It does leave one very tired and exhausted, doesn't it? This horrible pandemic. It's not a nice result."
Mr Hussain was the third member of his family to be admitted to hospital with Covid after they became ill towards the end of December 2020. His brother died first and then his father, who passed away while Mr Hussain was on a ventilator.
The Queen was told his wife called the ambulance after he had struggled to catch his breath, and Mr Hussain added: "I remember waking up one morning and just finding it really, really difficult to breathe.
"I remember waking my wife saying that I feel like there's no oxygen in the room. I remember me sticking my head out the window, just trying to breathe, trying to get that extra oxygen."
He was eventually put on a ventilator for seven weeks at the Royal London Hospital, and is still recovering, having recently dispensed with his wheelchair but now using a portable oxygen machine.
Mrs Hussain told the Queen at one point there were 500 friends and family from across the world on a Zoom call praying for her husband, and the monarch lightened the mood and made the couple smile when she asked: "So you have a large family, or a large influence on people?"
The issue of families and friends being unable to visit loved ones being treated in hospital was discussed a number of times during the Queen's video call with hospital staff, and at one point she said: "Of course not being able to see your relative was very hard."
Mireia Lopez Rey Ferrer, a senior sister who has worked at the hospital in Whitechapel, east London, since 2008, told the Queen about their commitment to the patients.
She said: "As nurses we made sure that they were not alone. We held their hands, we wiped their tears and we provided comfort.
"It felt at times that we were running a marathon with no finish line."
She added: "I look back to the last 18 months with great pride, pride not only in the care we provided to each and every single patient, that was in one of our hospital beds, but pride in each member of staff that every day they left their families at home despite their fears and worries and they came to work."
Polly Fitch, a clinical psychologist who ran the unit's family support team, described how information was put beside patients beds so medical staff knew their backgrounds and Imam Faruq Siddiqi, a chaplain who is part of the hospital's multi-faith team, said his presence was viewed with a sense of "hope" by families.
The head of state, who is the hospital's patron, said to the Imam: "It was obviously a very frightening experience to have Covid very badly, wasn't it?"
At the end of the call, the the Queen chatted to the construction team who created the unit on the hospital's 14th and 15th floors in quick time, and told them: "It is very interesting, isn't it, when there is some very vital thing, how everybody works together and pulls together - marvellous isn't it?"
When the team hailed the "Dunkirk spirit" that inspired them, the monarch replied: "Thank goodness it still exists."