The ability of the new coronavirus to spread is strengthening and infections could continue to rise, China's National Health Commission said on Sunday, with nearly 2,000 people in China infected and 56 killed by the disease.
A handful of cases have been reported outside China, including in Thailand, Australia, the United States and France, with health authorities around the world racing to prevent a pandemic.
The newly-identified coronavirus has created alarm because there are still many unknowns surrounding it, 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, and the virus is infectious during incubation, 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," Ma told a packed media briefing on the second day of the Lunar New Year holiday, adding that knowledge of the virus was limited.
Containment efforts, which have thus far included transportation and travel curbs and the cancellation of big events, will be intensified, Ma said.
The virus, believed to have originated late last year in a seafood market in the central Chinese city of Wuhan that was illegally selling wildlife, has spread to cities including Beijing and Shanghai. Hong Kong has six confirmed cases.
President Xi Jinping said during a politburo meeting on Saturday that China was facing a "grave situation".
On Sunday, China announced a nationwide ban on the sale of wildlife in markets, restaurants, and e-commerce platforms. Wild and often poached animals packed together in Chinese markets are blamed as incubators for viruses to evolve and jump the species barrier to humans.
Snakes, peacocks, crocodiles and other species can also be found for sale via Taobao, an e-commerce website run by Alibaba.
The U.S. State Department said it will relocate personnel at its Wuhan consulate to the United States and will offer a limited number of seats to private U.S. citizens on a Jan. 28 flight to San Francisco.
Japanese Prime Minister Shinzo Abe said on Sunday the government was working with Chinese authorities to arrange a charter flight for any Japanese nationals who wish to return from Wuhan.
The World Health Organisation this week stopped short of calling the outbreak a global health emergency, but some health experts question whether China can continue to contain the epidemic.
On Sunday, China confirmed 1,975 cases of patients infected with the new coronavirus as of Jan. 25, while the death toll from the virus has risen to 56, state broadcaster CCTV reported.
The outbreak has prompted widening curbs on movements within China, with Wuhan, a city of 11 million, on virtual lockdown, with transports links all-but severed except for emergency vehicles.
Health authorities in Beijing urged people not to shake hands but instead salute using a traditional cupped-hand gesture. The advice was sent in a text message that went out to mobile phone users in the city on Sunday morning.
Beijing is also postponing the reopening of the city's schools and universities after the Lunar New Year holiday, state radio reported. Hong Kong had already delayed the reopening of schools to Feb. 17.
Health officials in Orange County, California, reported that a third case of the new coronavirus had been registered in the United States, in a traveler from Wuhan, who was in isolation and in good condition.
On Saturday, Canada declared a first "presumptive" confirmed case in a resident who had returned from Wuhan. Australia confirmed its first four cases.
China has called for transparency in managing the crisis, after a cover-up of the spread of the deadly SARS virus eroded public trust, but officials in Wuhan have been criticised for their handling of the current outbreak.
"People in my hometown all suspect the real infected patients number given by authorities," said Violet Li, who lives in the Wuhan district where the seafood market is located.
"I go out with a mask twice a day to walk the dog - that's the only outdoor activity," she told Reuters by text message.
The outbreak has overshadowed the start of the Lunar New Year, when hundreds of millions of Chinese travel at home and abroad to be with families, with public events cancelled and many tourist sites shut.
Overall passenger travel declined by nearly 29 percent on Saturday, the first day of the Lunar New Year, from a year earlier, with air passengers down nearly 42 percent, a transportation ministry official said.
Many cinemas across China are also closed with major film premieres postponed, slashing revenues.
Cruise operators including Royal Caribbean Cruises, Costa Cruises, MSC Cruises and Astro Ocean Cruises said that they cancelled a combined 12 cruises that had been scheduled to embark from Chinese ports before Feb. 2.
Hong Kong Disneyland and the city's Ocean Park were closed on Sunday. Shanghai Disneyland, which expected 100,000 visitors daily through the Lunar New Year holidays, has already closed.
Airports around the world have stepped up screening of passengers from China, although some health officials and experts have questioned the effectiveness of such screenings.