It comes as the country's peak holiday travel season kicks off ahead of the Lunar New Year, sparking concerns over the spread of the viral strain and its possible impact on economic growth.
"It's highly likely we'll see this virus spread given that it appears there's some form of human-to-human transmission and given the scale of travel in the lead-up to Chinese New Year," said Alexandra Phelan, faculty research instructor in the microbiology and immunology department at Georgetown University.
"Looking further on, I think we're likely to have cases around China and also there will likely be cases in other countries as people travel," Phelan told CNBC on Monday.
While the Sars-virus first emerged in the central city of Wuhan in late December, the 139 new cases that appeared over the weekend in China showed new cases in the capital of Beijing in the north of the country, as well as in the southern city of Shenzhen, Reuters reported. This brings the total to more than 200 confirmed cases from the new coronavirus strain. Three of them have died.
Hundreds of millions of Chinese travelers are expected to travel both domestically and internationally as Lunar New Year starts this Saturday, igniting fears of a further spread of the virus and kindling memories of the fatal Sars pandemic in 2002 and 2003 that killed nearly 800 globally.
The Sars pandemic — also caused by a coronavirus — cost the global economy tens of billions of dollars.
On Monday, South Korea confirmed its first case of the new coronavirus in a Chinese woman who flew to Incheon International Airport from Wuhan.
Two cases have also been reported in Thailand and one in Japan. They involved two Chinese from Wuhan and a resident in Japan who had travel history to the city — where the virus is linked to a large seafood and animal market, suggesting that the virus had jumped from animals to humans, said the Centers for Disease Control and Prevention on its website.
However, some of the patients have not had exposure to the animal markets, "suggesting that some limited person-to-person spread is occurring," the CDC said Friday.
Airport authorities around the world have already stepped up health screening of travelers at their borders to pick up suspected cases. Measures include temperature screening.
However, as symptoms from the new Wuhan coronavirus infection are similar to that of other respiratory conditions, there will be "a lot" of travelers who would be wrongly picked up alongside, Phelan said.
"They can be a useful opportunity to provide people with information if they do feel sick ... but most of the time, border screening is actually a very expensive, not particularly effective way of actually preventing the spread of disease," said Phelan.
While the nature and severity of the new coronavirus is still under investigation, it could pose a major risk to Asia Pacific economies, experts said.
"Human-to-human transmission will be (the) tipping point, and mass movements in China during CNY (Chinese New Year) may be an unwelcomed accelerant," said Vishnu Varathan, Asia head of economics and strategy at Mizuho Bank.
In particular, the "fear factor" posed by the uncertainties that come with the new coronavirus could send economic activity grinding down rapidly and "hijack signs of bottoming/recovery in economic activity," Varathan said in an email to CNBC.
On Monday, shares of Chinese drugmakers and face mask-makers soared amid rising concerns over the outbreak.
Recent data out of China have suggested some bottoming out of the country's economy that was hit due to its bitter trade war with the U.S.
"The 2003 Sars crisis created a severe negative impact on GDP growth for the Chinese economy and also hit the economies of a number of Southeast Asian nations, including Malaysia, Singapore and Vietnam," said Rajiv Biswas, Asia Pacific chief economist at IHS Markit. There could also be a ripple effect elsewhere, he added.
"Since the 2003 Sars crisis, China's international tourism has boomed, so the risks of a global Sars-like virus epidemic spreading globally have become even more severe," Biswas said.
Sectors that are particularly vulnerable include retail, food and beverage, conferences, special events — such as the 2020 summer Olympics taking place in Tokyo — and aviation, said Biswas.