Li Ding, 66 and his son Li Zichao, 28, must have passed on the infection among themselves, a representative of the Cho Ray Hospital said Thursday. This is Vietnam's first confirmed cases of individuals infected with the new coronavirus (nCoV) after it was first detected in Wuhan City last December.

Ding arrived in Hanoi from Wuhan on January 13, before proceeding to Nha Trang in the central province of Khanh Hoa, said doctor Nguyen Ngoc Sang of the Department of Tropical Diseases. His son Zichao, who had resided in Long An Province for the previous four months, went to visit him in Nha Trang. Both of them traveled to Saigon and the neighboring Long An later, said Sang.

Ding developed a fever on January 17, and Zichao followed suit on January 20. Both were admitted to the Cho Ray Hospital Wednesday night.

"This infection is a serious matter," said Deputy Health Minister Nguyen Truong Son.

The patients’ fever has subsided and they are now able to consume food and drinks.

As both patients have traveled through different places in the country by plane, train, taxi, they could have contacted with many people and there's a chance they have spread the disease, doctors said.

A pneumonia outbreak, caused by a new strain of the coronavirus family that caused SARS and MERS, first surfaced in Wuhan City, China last December.

By January, the disease has spread to other countries and territories: Thailand, South Korea, Japan, Taiwan, Macau, Hong Kong, the United States and Singapore.

China’s National Health Commission has confirmed 571 cases and 17 deaths as of Wednesday.

The World Health Organization (WHO) has said that an animal appears most likely to be the primary source of the virus. China says the virus could have come from a market in Wuhan where wildlife was traded illegally.

The Vietnamese Ministry of Health has warned people to keep their distance from people with acute respiratory infections and wear a mask when talking to them. Equipment to monitor arriving passengers’ body temperature have been installed at airports in Hanoi, Saigon, Da Nang and Cam Ranh in central Vietnam