The 22-year-old man so far showed no sign of pneumonia, said Nguyen Thanh Trung, deputy director of Da Nang Hospital on Thursday. The patient is one of two Chinese from Wuhan City quarantined after displaying fevers.

The other, a 3-year-old boy traveling in the same group, suffered from a light fever and has since been discharged.

Test results from throat swabs and blood serum samples at Nha Trang Pasteur Institute confirmed both were not infected with a type of mystery pneumonia first reported in Wuhan last December that has since spread across China, Thailand and Japan.

This is the first case of sick foreigners entering Vietnam since the acute pneumonia outbreak in China, which has infected 41 in Wuhan and killed a 61-year-old man.

The disease, possibly caused by a newly emerging strain of the coronavirus family that caused SARS (Severe Acute Respiratory Syndrome) and MERS (Middle East Respiratory Syndrome), has infected a Chinese woman in Thailand and a man in his 30s in Japan this month, Reuters reported.

There could be limited human-to-human transmission, potentially among families, said acting head of World Health Organization’s emerging diseases unit Maria Van Kerkhove. Anti-virals are being considered and could be "re-purposed" to deal with the new virus, she added.

Airports in Hanoi, Ho Chi Minh City, Da Nang and Khanh Hoa Province, the latter two major destinations for Chinese tourists, have installed equipment to monitor arriving passengers' body temperature.

Vietnam’s Ministry of Health has warned people to keep their distance from those with acute respiratory infections and wear a mask when in conversation.

Keeping warm and maintaining personal hygiene, especially the regular washing of hands using soap and gargling with antiseptic rinse, are also recommended.

Those traveling from Wuhan showing signs of fever, coughing or difficulty in breathing should visit the nearest medical facility, the ministry said.