At Saigon’s Cho Ray Hospital, Li Zichao, 28, was tested three times including on Monday and turned up negative every time. He had been at the hospital for six days.

Zichao is able to breathe without the assistance of a respirator and eats food normally, Dr Nguyen Tri Thuc, the hospital director, said.

His father, Li Ding, 66, is still receiving treatment. He sleeps and eats without difficulty and his organs are functioning well, but he still needs a ventilator.

Ding's temperature became normal on Saturday night, three days after being admitted, but tests on Monday still showed positive for the virus, Thuc said. He is in quarantine.

The testing protocol goes like this: One day after the fever breaks, the hospital takes the patient’s sample for testing for the new coronavirus (nCoV). If the result is negative, another test is done three days later, and the patient is discharged if that is negative too.

The two men were Vietnam's first confirmed cases of nCoV infection after it was first detected in Wuhan in China last December.

Ding arrived in Hanoi from Wuhan with his wife on January 13 before flying to Nha Trang four days later and developing a fever.

Zichao, who has been living in Long An Province for the last four months, went to visit him in Nha Trang. The three then came to Saigon and travelled to neighboring Long An by taxi.

Zichao developed a fever on January 20, three days after his father. Both were admitted to the Cho Ray Hospital on January 22. Ding’s wife tested negative.

Since they traveled to various places in the country by plane, train and taxi, there is a chance they have spread the disease, doctors said.

The nCoV virus has spread from mainland China to Thailand, South Korea, Japan, Taiwan, Macau, Hong Kong, the U.S., Singapore, Malaysia, France, Canada and Vietnam.

Chinese authorities said as of Tuesday morning, January 28, 106 people had died of the disease. The number of confirmed cases of individuals infected with the virus reached over 4,500.

In Vietnam, no local has contracted the nCoV yet.