The ability of the new coronavirus to spread is strengthening and infections could continue to rise, China's National Health Commission said yesterday, with more than 2,000 people in China infected and 56 killed by the disease.
Health authorities around the world are racing to prevent a pandemic after a handful of cases of infection were reported outside China, including in Thailand, Australia, the United States and France.
The mayor of Wuhan in China, the epicentre of the outbreak, said he expected another 1,000 new patients in the city, which was stepping up construction of special hospitals.
The newly identified coronavirus has created alarm because much about it is still unknown, such as how dangerous it is and how easily it spreads between people.
It can cause pneumonia, which has been deadly in some cases.
China's National Health Commission Minister Ma Xiaowei said the incubation period for the virus can range from one to 14 days, during which infection can occur, which was not the case with Severe Acute Respiratory Syndrome (Sars).
Sars was a coronavirus that originated in China and killed nearly 800 people globally in 2002 and 2003.
"According to recent clinical information, the virus's ability to spread seems to be getting somewhat stronger," Mr Ma told reporters.
The Lunar New Year holiday, traditionally celebrated by hundreds of millions of Chinese travelling around the country and abroad to see family, began on Friday but has been severely disrupted by the outbreak.
Mr Ma said China would intensify its containment efforts, which have so far included transportation and travel curbs.
The country may extend the week-long Lunar New Year holiday, state broadcaster CCTV reported, citing a meeting hosted by Chinese premier Li Keqiang.
The virus, believed to have originated late last year in a seafood market in Wuhan that was illegally selling wildlife, has spread to cities including Beijing and Shanghai.
Hong Kong has six confirmed cases.
The World Health Organisation this week stopped short of calling the outbreak a global health emergency, but some health experts question whether China can contain the epidemic.
Chinese President Xi Jinping described the situation as "grave" on Saturday.
China confirmed 2,051 cases of infection as of 7pm (11am GMT) yesterday, while the death toll from the virus remained at 56, state broadcaster CCTV reported.
Health officials in Orange County, California, reported that a third case had been registered in the United States in a traveller from Wuhan, who was in isolation.
On Saturday, Canada declared a first "presumptive" confirmed case in a resident who had returned from Wuhan.
Australia, meanwhile, confirmed its first four cases.