He had come into contact with dozens of people in HCMC before leaving the country, local officials said.

Authorities learnt of this special case Sunday evening, Nguyen Tan Binh, Director of HCMC Health Department said at a Monday afternoon meeting.

He said that the Covid-19 illness might have recurred within the patient or he might have got infected again after he was discharged from the hospital in Da Nang.

"From now on, visitors to Ho Chi Minh City must be closely monitored," Binh said.

Reports had said that female "Patient 50," a 50-year-old Vietnamese man being treated in Hanoi, and "Patient 91," a 43-year-old British man in HCMC, had also tested positive after negative results and they are still undergoing treatment.

Meanwhile, a Reuters report Monday said at least 116 people initially cleared of the novel coronavirus had tested positive again in South Korea.

The report quoted Jeong Eun-kyeong, director of the Korea Centers for Disease Control and Prevention (KCDC), as saying the virus may have been reactivated rather than the patients being re-infected.

It also cited other experts’ opinions that "faulty tests may be playing a role, or remnants of the virus may still be in patients’ systems but not be infectious or of danger to the host or others."

Post discharge movements

The 66-year-old British man had flown into Hanoi from London on the Vietnam Airlines flight VN54 on March 2.

The British man was tracked down by local authorities as he toured the country. He tested positive on March 8 and was treated at Da Nang Hospital until he was discharged on March 27 after testing negative three times. He was later quarantined at a hotel in Son Tra District for 14 days.

On April 10, he flew from Da Nang to HCMC and stayed at a hotel on Hong Ha Street in Tan Binh District while waiting to fly back to the U.K. His samples were taken and the result came out positive Sunday evening, but he’d already departed for home by then.

The hotel where he stayed has been disinfected. Fourteen people who came into close contact with him have been sent to centralized quarantine facilities. Three hotel employees as well as 31 guests have been quarantined at the hotel and are being medically supervised.

Authorities have contacted Vietnam Airlines to isolate and conduct tests on those who sat near him on the flight he took.

Le Thanh Liem, Standing Vice Chairman of HCMC People's Committee, said: "The Ministry of Health has not officially announced this, but the city does not hide the fact and is providing the information to work with people who are relevant to the case. It would complicate things if any of the 14 people who came into close contact with the man tests positive, leading to other infections."

As of Tuesday morning, Vietnam had recorded 265 Covid-19 cases. Of these, 145 have been discharged from hospitals.

HCMC alone has recorded 54 cases and 40 discharges.

Among the active cases, "Patient 91", a British pilot who works for Vietnam Airlines, is critically ill and is on ventilator support.

There are two suspected cases who are awaiting test results, while 244 people are in centralized quarantine facilities and 411 others are home quarantined.

Binh has directed local authorities to continue monitoring all people entering the city, including screening of passengers arriving at the Saigon Railway Station and the domestic terminal of the Tan Son Nhat Airport, where international flights have been suspended. Quarantine facilities must also be disinfected after occupants have left, he said.