BEIJING (2nd UPDATE) - China put millions of people on lockdown on Thursday in two cities at the epicenter of a coronavirus outbreak that has killed 17 people and infected more than 630, as authorities around the world worked to prevent a global pandemic.
Health officials fear the transmission rate could accelerate as hundreds of millions of Chinese travel at home and abroad during week-long holidays for the Lunar New Year, which begins on Saturday.
The previously unknown virus strain is believed to have emerged late last year from illegally traded wildlife at an animal market in the central Chinese city of Wuhan.
Most transport in Wuhan, a city of 11 million people, was suspended on Thursday and people were told not to leave. Hours later, neighboring Huanggang, a city of about 7 million people, announced a similar lockdown.
"The lockdown of 11 million people is unprecedented in public health history," Gauden Galea, the World Health Organization's (WHO) representative in Beijing, said.
The newly-identified coronavirus has created alarm because there are a number of unknowns surrounding it. It is too early to know just how dangerous it is and how easily it spreads between people.
There is no vaccine for the virus, which can spread through respiratory transmission. Symptoms include fever, difficulty breathing and cough, similar to many other respiratory illnesses.
Three research teams are to start work on developing a vaccine, a global coalition set up to fight diseases said.
As well as restricting movement, Wuhan plans to build a new hospital in six days to treat patients, Beijing News reported, citing a construction company source.
Other cities were also taking steps to contain the virus.
Nearby Ezhou shut train stations. Beijing cancelled large gatherings, including two Lunar New Year temple fairs, and closed the Forbidden City, the capital's most famous tourist attraction, to visitors until further notice.
Airports worldwide were screening passengers arriving from China. Hong Kong, which has two confirmed cases, is turning two holiday camps into quarantine stations as a precaution. Taiwan has banned anyone from Wuhan from going to the island.
Chinese people had their own ways of protecting themselves.
"I go straight to where I need to go, and then I go home," said 79-year-old Li Meihua, from behind a mask, on the streets of Shanghai. "I'm also maintaining a cleaner diet, I've turned vegetarian."
Preliminary research suggested the virus was passed on to humans from snakes, but government medical adviser Zhong Nanshan has also identified badgers and rats as possible sources.
Some experts believe the virus is not as dangerous as previous coronaviruses such as Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory Syndrome (MERS).
"The early evidence at this stage would suggest it's not as severe," Australia's Chief Medical Officer Brendan Murphy said.
Jeremy Farrar, director of research charity Wellcome Trust, said: "We don’t want to overstate the panic here because there is so much uncertainty. We want to keep a sort of calm, moderated approach to it, but we do have to take this incredibly seriously because you don’t often get an animal virus coming into humans, passing between humans and being spread by the respiratory route."
The WHO will decide on Thursday whether to declare the outbreak a global health emergency, which would step up the international response.
If it does so, it will be the sixth international public health emergency to be declared in the last decade. Its Emergency Committee meeting was under way in Geneva and a news conference is expected after 1800 GMT.
Michael Ryan, head of WHO emergencies program, said on Wednesday, that according to data presented from China, almost three quarters of the cases were in people aged over 40, with some 40% having underlying health conditions.
Giving the latest details on infections in China, state television said 634 cases had been confirmed. By the end of Wednesday, China's National Health Commission confirmed 17 dead.
Of the known cases worldwide, Thailand has confirmed four, while Singapore, Japan, South Korea, Taiwan and the United States have reported one each.
Vietnam said two Chinese citizens had tested positive and an Indian nurse working in Saudi Arabia has been infected, India said.
To try to stem the outbreak, Wuhan shut all urban transport networks and suspended outgoing flights from 0200 GMT. Domestic media said some airlines were operating after the deadline.
Its Hankou railway station was nearly deserted, state broadcasts showed. State media reported highway toll booths around Wuhan were closing, effectively cutting off road exits. Guards were patrolling highways, one resident said.
As the city slipped into isolation, residents thronged hospitals for checks and scrambled for supplies, clearing out supermarket shelves and queuing for petrol.
Authorities in Huanggang ordered entertainment venues including cinemas and internet cafes to close.
In contrast with its secrecy over the 2002-03 SARS that killed nearly 800 people, China's Communist Party government has provided regular updates to avoid panic ahead of the holidays.
During a visit to Wuhan, Vice Premier Sun Chunlan said authorities needed to be open about the virus and efforts to contain it, the official Xinhua news agency said.
Despite China's response, world shares fell on Thursday, led by the biggest tumble in Chinese stocks in more than eight months. China's yuan fell to a two-week low.
The economic impact of such outbreaks are hard to quantify but a 2006 estimate by the International Air Transport Association (IATA) calculated that SARS shaved just over 1 percentage point off the GDP of China in 2003.
Many Chinese were cancelling trips, buying face masks and avoiding shopping centres. The release of seven Chinese movies over the Lunar New Year has been postponed.