Covid-19 patients who rush back to work could find themselves so exhausted they need to take further time off, a respiratory consultant has said.

Dr Jon Bennett, a consultant at Glenfield Hospital in Leicester and chairman of the British Thoracic Society, said it can take several weeks to recover from coronavirus even after the major symptoms disappear.

The medic, who has treated around 60 to 70 patients with Covid-19, told the PA news agency that many factors affect recovery, including a patient’s age, underlying health conditions and the severity of their illness.

Dr Bennett is himself still recovering from coronavirus, after suffering sleepless nights with muscle pain, a headache and mild cough.

He said many patients needing oxygen for Covid-19 had evidence of pneumonia, which can have long-lasting effects.

“With pneumonia, the bug comes, the body fights off the virus and (that) may last a few days, but the lungs get filled up with shall we say bruising and it can take several weeks for the lungs to sort that out.

“For some people, the symptoms can take several weeks to settle.

“People suffer fatigue and lethargy and it can take six weeks to recover from it.

“For some that have been to critical care, it can take longer and they may have permanent damage to their lungs.

“If a patient doesn’t have pneumonia, then in theory it should be a quicker recovery.

“In these cases, it will be the overall effect of the disease that will be thing to recover from – the fatigue and so on.

“The underlying age and fitness of the person makes a big difference.

“Younger people bounce back quicker.

“When it comes to people’s underlying health problems – those who are frailer may not recover to the level they were before even before they had Covid.

“Psychology also has a role to play as well.

“We do find some people want to get back to work too soon.

“We have had a few people who went back to work but they were so knackered they had to go back home again.

“They’ve not been on 100% top form, so we’ve told them to go home and make a fuller recovery.”

Duncan Young, professor of intensive care medicine at the University of Oxford, said UK evidence suggests the commonest stay on an intensive care unit (ICU) for patients who survive Covid-19 is four days, but a quarter stay for eight or more days.

“In general the time in hospital depends on what co-morbidities a patient has, what the acute illness is that required ICU treatment, and the duration and intensity of ICU treatment.”