His condition, however, remains critical and he remains on life support.

Luong Ngoc Khue, director of the Administration of Medical Examination and Treatment under the Health Ministry, said the Hospital for Tropical Diseases in Ho Chi Minh City has "fulfilled its mission of treating the British man," tagged as "Patient 91."

In the past 19 days, he has tested negative for the virus five times.

"Now it can be confirmed that he is free from the novel coronavirus," Khue said.

"Patient 91," 43, is a pilot working for national flag carrier Vietnam Airlines. He was admitted to the hospital on March 18.

City authorities later confirmed that he turned out to be the source of transmission at its biggest Covid-19 hotspot, the Buddha Bar & Grill in Thao Dien Ward, District 2, which saw 19 people, including many foreigners, get infected.

His condition worsened quickly and he has been hospitalized for more than two months. At present, he has been completely reliant on a life support machine called extracorporeal membrane oxygenation (ECMO).

Doctors said he suffers from a blood clotting disorder and cytokine storm syndrome, an intense immune response where the immune system releases a lot of cytokines through the bloodstream, which works against the body.

The HCMC Hospital for Tropical Diseases announced Tuesday that 20-30 percent of his lungs could now function, compared to just 10 percent a week ago.

However, hospital director Nguyen Vinh Chau said a lung transplant is still on agenda, as decided by the Health Ministry last week.

For now, the patient is still suffering from pleural infection and is not ready for a transplant. Free of the virus, he has been transferred to the Cho Ray Hospital for further treatment.

Experts from the ministry will work together to decide whether he needs more organ transplants besides his lungs, because some of them have been damaged, Chau said, without elaborating.

The nation has spent about VND5 billion ($215,000) over the past two months on the British man, and the estimated cost of a lung transplant is about VND1.5-2 billion ($65,000 to 86,000).

The Viet Duc Hospital in Hanoi has been asked to get ready to operate once the patient is eligible for a lung transplant and a matching donor is found.

So far, 60 people in Vietnam have volunteered to donate part of their lungs to the British man, but doctors said they would give priority to donations from brain-dead donors.

The situation is complicated by the fact that the pilot had said he has no relatives when he was still conscious. Under current regulations in Vietnam, all surgical interventions must be agreed to by the patient or the patient's authorized representative.

Vietnam has not recorded any new Covid-19 patient since Monday evening. The nation’s Covid-19 tally stands at 324, including 60 active patients. The rest have recovered.