The coronavirus was detected in Wuhan three weeks ago.
Police, SWAT teams and paramilitary troops guarded Wuhan's train station as last-minute travellers arrived, only those holding tickets for the last trains allowed to enter.
Meanwhile, in Geneva, the World Health Organization's emergency committee is meeting to assess the global risks posed by the virus and decide if it should be declared an worldwide public health emergency - as happened with swine flu and Ebola. People have been lining up to buy them at pharmacies, which limited sales to one package per customer.
A map created by USA researchers is tracking in real-time a virus in China that has sickened hundreds of people and resulted in at least 17 deaths. Medical workers wore protective suits outside a hospital where some patients with the viral respiratory illness are being treated. Tedros said he is in daily contact with Chinese authorities.
From 10 a.m. Thursday, the city will no longer be operating its bus, subway, ferry, and long-distance transit services until further notice, the announcement said.
On Tuesday, Wuhan officials introduced a mandatory mask policy at local restaurants, hotels, movie theaters, shopping malls, and parks, among other places.
Animals are suspected to be the primary source of the outbreak, with Chinese health officials saying that the virus originated from the market where wild animals were illegally sold.
China's health commission says it can not confirm human-to-human transmission of the virus but the possibility "cannot be excluded". "It really came down to their interpretation of what is 'international spread, '" Phelan says.
Almost two decades after the disastrously handled SARS epidemic, China's more open response to the new virus signals its growing confidence and greater awareness of the pitfalls of censorship, even though the government remains as authoritarian as ever.
With the virus spreading so rapidly, health fears have rocketed regarding travel.
"There's not a lot of other global cases reported yet", Gardner said.
The first cases in the Wuhan outbreak were connected to people who worked at or visited a seafood market, which has since been closed for an investigation. Outside of China, cases have been reported in the U.S., Taiwan, Thailand, South Korea and Japan, the Centers for Disease Control and Prevention reported this week.
"We are still in the process of learning more about this disease", Gao Fu, the CCDC head and an academician of the Chinese Academy of Sciences, said at a Wednesday news conference. Another important thing to keep in mind is that novel coronavirus in many ways resembles influenza, so people may not realize they have it.
A global emergency is the highest level of alarm the World Health Organization can sound and has previously been used in response to swine flu, Zika virus and Ebola.
Wuhan is starting to look like a city in quarantine.
A number of countries, including the United Kingdom, are screening passengers who arrive from Wuhan, China.
One veteran of the SARS outbreak said that while there are some similarities in the new virus - namely its origins in China and the link to animals - the current outbreak appears much milder. "The committee felt it was a little too unprecise to very clearly state that it was time" to recommend declaring a PHEIC, Houssin said.