Doctors have warned that tens of thousands of recovered COVID-19 patients will need to be recalled to hospital to undergo checks for possible permanent damage to their lungs.

The medical experts, who spoke with BBC, said such patients could be left with lung scarring known as pulmonary fibrosis.

Common symptoms of pulmonary fibrosis — which cannot be cured — include severe shortness of breath, coughing and fatigue.

Anthony McHugh, a retired taxi driver, who has endured similar experience, recounted how he was admitted to hospital on March 6, after showing symptoms of the virus.

The 68-year-old would later be discharged mid-April after he was treated from of the disease. But about two months after leaving the hospital, McHugh said he still suffers breathing difficulties.

“It’s little things like walking up the stairs or watering the flowers outside. I start bending down and I have to stop,” he told the news outlet.

An X-ray conducted on McHugh’s lungs six weeks after he left the hospital revealed thin white lines known as reticular shadowing, that could indicate the early signs of scarring or pulmonary fibrosis.

He is billed to undergo another scan after 12 weeks to ascertain if the suspected scarring on his lungs has worsened.

The development, Sam Hare, an executive committee member of the British Society of Thoracic Imaging (BSTI), said is something to worry about.

Hare, who is also an advisor to the Royal College of Radiologists, however, added that there are no ample evidences yet to ascertain the extent and rate of lung damage caused by COVID-19

“With all these cases, we can’t say for certain at the moment,” he said.

“But usually with a virus or infection at six weeks, you would expect the scan to have returned to normal. It hasn’t and that’s the worry.”

A study conducted in China and published in March revealed 66 of 70 patients still had some level of lung damage after being discharged from hospital, BBC reports.

Several radiologists in the UK, who corroborated with the study, pointed out that about 30% of patients discharged of COVID-19 seem to show symptoms of lung scarring.

“In the six-week scans we’re seeing, so far I would say between 20% and 30% of patients who have been in hospital appear to show some early signs of lung scarring,” Hare added.

A similar trend with Sars and Mers — earlier coronavirus outbreaks — showed 20% and 60% of recovered patients also nursed issues related to pulmonary fibrosis.

Health experts said there’s need to thinker how to address the problem considering the fact that COVID-19 has spread to countries across the world.

“We now need to understand how big the problem is and when we should intervene with treatment,” said Gisli Jenkins, a professor at the National Institute for Health Research (NHS) in England, who is running assessment clinics for those discharged from hospital with COVID-19.

“My real concern is that never before in our lifetime have so many people been subject to the same lung injury at the same time.”

Due to the concerns raised by doctors, the NHS has announced that it is opening specialist rehabilitation centres.