Almost all flights at Wuhan's airport have been cancelled and checkpoints block the main roads leading out of town. Reuters reports that a handful of airlines were operating past the 10:00 am deadline.
"The virus is now spreading at an alarming rate". Of eight known cases worldwide, Thailand has confirmed four, while Singapore, Japan, South Korea, Taiwan and the United States have reported one each. There is no vaccine or specific treatment for the new virus.
Prof Paul Hunter, professor in medicine at the University of East Anglia, said: " I think it unlikely that the Wuhan coronavirus will be cause a major public health issue in the United Kingdom in large part because of our existing health system.
Airports worldwide were screening passengers arriving from China.
A screen showing the body temperatures of arriving passengers is seen at a health monitoring station as a precautionary measure to protect against the possible spread of coronavirus outbreak at Hong Kong International Airport ahead of the Chinese New Year in Hong Kong on January 23, 2020. It can cause pneumonia, which has been deadly in some cases.
Typical symptoms include a runny nose, cough, sore throat, headache and fever, which can last a few days.
Most of the fatalities have been in elderly patients, many with pre-existing medical conditions, the World Health Organization said. The health commission in Hebei, a northern province bordering Beijing, said an 80-year-old man died after returning from a two-month stay in Wuhan to see relatives.
Viruses can make the jump from animals to humans, especially when wild animals are kept and sold in food markets, as is alleged to be the case in Wuhan.
The death toll stands at 18, with all fatalities occurring at the epicentre of the outbreak in Wuhan, the capital of Hubei province. It did not give further details.
Health officials fear the transmission rate will accelerate as hundreds of millions of Chinese travel at home and overseas during week-long holidays for the Lunar New Year, which begins on Saturday. On Thursday, the U.S. Centers for Disease Control and Prevention said people should avoid nonessential travel to Wuhan.
"What choice do I have?" Mounting fears about the outbreak have roiled financial markets, and the Shanghai Composite Index had the worst end to a Lunar Year in its three-decade history.
Members of the emergency committee, having taken two days of meetings to reach Thursday's decision after postponing it once Wednesday, remains "very divided, nearly 50-50" on the decision, its chairman said.
As part of the restrictions, some sections of the Great Wall near Beijing will be closed from Saturday, state media said.
Major public events were canceled, including traditional temple fairs popular during the Lunar New Year.
China's airline authority urged airlines to "reduce flights" into Wuhan, and said 288 inbound flights were cancelled Thursday morning.
World Health Organization country representative Gauden Galea tells The Associated Press that closing off a city of that size to try to stem an outbreak is new to science and that it's too early to gauge results.
Asked whether China would consider any request from the respective countries to move their citizens out of Wuhan, Chinese foreign ministry spokesman Geng Shuang said, "We always help foreign consular officials in China in their official jobs, we offer them all the assistance and convenience necessary and we work to guarantee foreign citizens' legitimate rights and interest in China".