The 50-year-old woman was diagnosed with the disease and hospitalized in late February and then spent 16 weeks on extracorporeal membrane oxygenation (ECMO) support, which involves circulating a patient's blood through a machine that adds oxygen to red blood cells.

That's the longest that any COVID-19 patient in the world has spent on ECMO support, her doctors said.

Various drugs such as the anti-malarial hydroxychloroquine, the HIV treatment Kaletra and steroids failed to stop her pulmonary fibrosis - scarring in the lungs - from worsening, said Dr Park Sung-hoon, professor of pulmonary and critical care medicine at Hallym University Sacred Heart Hospital.

That left few options other than a lung transplant.

"The probability of success in lung transplants on ECMO patients is 50%, and fortunately, our patient was well prepared before the surgery when we found the donor," said Dr Kim Hyoung-soo, director of the hospital's ECMO program, who was in charge of the surgery.

The patient declined to be identified or interviewed.

The doctors who conducted the eight-hour surgery described her destroyed lungs as hard like rock.

She had an acute respiratory distress syndrome (ARDS) when she came to hospital, Park said, and could not live without the ECMO machine's help.

ECMO is typically used on patients who need more help than ventilators can provide, and who are considered to have a 90% chance of dying. Half of patients recover in two to three weeks on ECMO, and a lung transplant is considered for those who don't, Kim said.

The surgery was the ninth after six similar surgeries in China, and one each in the United States and Australia, the hospital said.

Lung transplants are less common that other transplants in South Korea, with 92 of them in 2018, compared with 2,108 kidney and 176 heart transplants, according to the Korea Centers for Disease Control and Prevention.

Lee Sun-hee, a head nurse of the ECMO program who has cared for the patient since February, said the woman seemed to have a stronger-than-usual will to live, in part driven by being a mother of two.

"She told us, 'I'm grateful for the sunshine, for the moonlight. I'm so grateful that I am breathing'," Lee said.

Lee said the woman already knows the first thing she wants to do when released from the hospital:

"To get a nice bath."

Doctors said she would be discharged when her chest muscles are strong enough to support her breathing.