Lucy Williamson
BBC News Paris Correspondent

The Chinese Embassy in Paris has told the BBC that they are trying to locate a woman from the Wuhan area who said on social media that she had taken medication to suppress signs of the virus in order to enter France.

There is no confirmation of whether she is still in France, or whether she does have the virus.

The woman had reportedly passed through screening at customs while flights out of Wuhan were still operating and then posted pictures of herself eating at a Michelin-starred restaurant in France and described how she had managed to get there.

She has been widely criticised by other Chinese social media users, the South China Morning Post reports.

All the fatalities so far have been in Hubei province, of which Wuhan is the capital.

But Wuhan is also a major transport hub, and non-fatal cases of the virus appear to have spread from the city to other provinces, mainly in the east of the country.

Apart from the city's airports, it's also well-connected by railway to major population centres - including Shanghai and Beijing.

Michelle Roberts
Health editor, BBC News online

At the moment, there is no vaccine that can protect people against this type of coronavirus, but researchers are looking to develop one.

It is a new strain that hasn't been seen in humans before, which means doctors still have lots to learn about it.

Owen Amos
BBC News, Singapore

Image source, Getty

Can you quarantine an entire city? And if you can - does it work?

Wuhan is a huge place - the 42nd biggest city in the world, according to UN data - and cannot easily be turned into an isolation ward.

"The only way you could do it, realistically, would be to ring-fence the city with the PLA [Chinese military]," says Professor Adam Kamradt-Scott, a health security expert from the University of Sydney.

But even if they do it, where - literally - would they draw the line? Like most modern cities, Wuhan sprawls into smaller towns and villages.

Gauden Galea, the World Health Organization's representative in China, puts it more bluntly.

"To my knowledge, trying to contain a city of 11 million people is new to science," he told the Associated Press. "We cannot at this stage say it will or it will not work."

And even if it proves possible to shut the stable door on Wuhan, the horse may already have bolted.

• Read more: How do you quarantine a city - and does it work?

Kerry Allen
BBC Monitoring, Chinese Media Analyst

Some criticisms are appearing in Chinese media about why the authorities were slow to respond to the outbreak.

The Chengdu Business Daily, external is asking “why didn’t Wuhan close the city earlier” and Hu Xijin, the editor of prominent newspaper Global Times acknowledges that there was a “failure” to contain the virus, external, saying he was "worried that some places, while attaching great importance to meetings and slogans, have not really been mobilised to deal with a large public health battle”.

Elsewhere, The Paper also interviews a couple, who say they suspect they may have the virus, external, but have waited days on end without being diagnosed or quarantined.

James Gallagher
Health and science correspondent, BBC News

Don’t rule it out yet, but this is not a clear-cut decision.

After a full day of deliberations on Wednesday, the World Health Organization’s emergency committee was split on whether to declare a global emergency. Instead it is spending another day assessing the evidence.

The challenge is the facts are changing as scientists grapple with key questions such as how easily the coronavirus spreads from person to person and what is the true scale of the outbreak beyond those appearing in hospital.

Dr Tedros Ghebreyesus, WHO director-general, said it was an “evolving and complex situation” and that “appropriate consideration of all the evidence” was needed.

There are three tests that need to be passed before declaring a public health emergency of international concern. It must be an “extraordinary event” with a risk of “international spread” that requires a “co-ordinated international response”.

The mayor of Wuhan has acknowledged that officials were too slow to control the disease.

Zhou Xianwang said the authorities didn't fully understand the danger of the virus -- or how quickly it would spread.

The mayor has been criticised by some residents of Wuhan - a major transport hub - who say he should have acted quicker.

Anna Jones
BBC News, Singapore

Image source, EPA

The Beijing Daily newspaper reports that Beijing has cancelled large-scale events including some Chinese New Year celebrations as a precaution against the virus spreading.

The cancelled events include many temple fairs, visits to which are a popular new year activity.

What happens at Chinese New Year?

This virus couldn’t have emerged at a worse time for Chinese people. The lunar new year - the biggest holiday of the year - is this weekend.

That’s when people across China, as in all countries that mark the lunar calendar, get together with their families for reunion dinners and celebrations.

In China alone, hundreds of millions of people travel often vast distances to get home. For many it’s their only break in the year and the only time to see their loved ones.

That makes for the world's biggest annual human migration - before the coronavirus outbreak some 440 million rail journeys were expected to be made and nearly 80 million people were expected to take flights.

For those in Wuhan, spending the holiday cooped up at home instead, and worrying about the virus, will be a miserable experience for many, many people.

Grace Tsoi
BBC World Service, Hong Kong

I’ve been trying to look for people in Wuhan to talk about how life is like after the city was put into a lockdown, but many are not willing to speak on record for fear of possible repercussions.

The city is quiet – also partly because the Chinese New Year is coming this Saturday. Wuhan is a major transportation hub and home to many universities.

People are worried about the spread of the disease, but things are still calm for now. Some of the people told me they were going to stay home during the Chinese New Year holiday, instead of visiting relatives, to minimise contact with others.

Image source, Getty Images

Most are wearing face masks now, which didn’t happen before – and some are blaming the government for not revealing the severity of the outbreak. One told me only pharmacies and supermarkets are still open.

But hospitals are full and patients need to wait for four to five hours just to see doctors, even when they display respiratory symptoms.

There have been cases in several Chinese cities and also in other countries including Thailand and the US.

"The lockdown of 11 million people is unprecedented in public health history," an official from the World Health Organisation told Reuters news agency.

Gauden Galea, a representative of the organisation in Beijing, added that "it is certainly not a recommendation the WHO has made," the news agency said.

But the dramatic move shows "the commitment to contain the epidemic", he said.

The WHO, meanwhile, is considering whether or not to declare a global emergency over the outbreak, though it opted not to do so on Wednesday.

Briton Thomas Crosby has told the BBC he was surprised there wasn't more screening as he travelled from Wuhan to London.

Authorities in Wuhan have since suspended all public transport into and out of the city.

Residents in Wuhan are feeling the stress of the outbreak.

"We are feeling as though it is the end of the world," AFP quoted one local as saying. "We really need everyone's help."

One taxi driver working the streets told the news agency: "It's very dangerous to be outside at this moment but we need to earn money" – and that drivers had tripled their usual fares.

Some news organisations have pulled their teams from Wuhan. CBS News left just before the lockdown began last night – but their reporter said that almost every person in the airport was masked with whatever they could find to protect themselves.

That same caution is reflected by the officials.

Officials are using special cameras at the airport to check passengers' body temperatures – and if they did get to leave, were screened again upon arrival in places like Beijing and Hong Kong.

Image source, AFP

Another city, Ezhou - a city of a million people across the Yangtze river from Huanggang - said on Thursday it had shut its train stations.

Huanggang is the second city to have major restrictions placed on it as authorities try to halt the spread of the newly-discovered virus.

With a population of more than seven million people, it's a major population centre - London, for example, has about eight million residents.

It's situated about 70km from Wuhan, the first city to be put on lockdown. Reuters reports there have been 12 cases there up to the end of Monday.

For residents of Huanggang, the bus and train networks will be closed at the end of Thursday, local time (five hours from now).

Citizens have been asked not to leave by other means, either.

And in the city itself, normal life is set to be disrupted, as public spaces like cinemas and cafes will be shut.

In a little more than three weeks, we have gone from the first case reported to seeing two major cities going into lockdown. Here's how we got to this point.

• 31 December: China alerts the World Health Organisation about a spate of pneumonia-like cases in Wuhan
• 1 January: The seafood/animal market believed to be at the centre of the outbreak is closed
• 9 January: WHO says the infection is caused by a new type of coronavirus
• 11 January: First death confirmed
• 13 January: Virus spreads abroad, with a suspected case in Thailand
• 20 January: Outbreak spreads to Beijing, Shenzhen and Shanghai; Chinese officials confirm human-to-human transmission
• 21 January: US authorities announce the first case in North America - a man who had visited Wuhan
• 22 January: Death toll climbs to 17, with more than 500 cases confirmed

• 23 January: Wuhan, population 11 million, goes into lockdown. Authorities announce similar measures in the nearby city of Huanggang from midnight local time

As news breaks of China's coronavirus spreading to other cities, we're going to bring you live coverage of developments over the next few hours.

Chinese authorities had already locked down nine million people in the city of Wuhan, the suspected origin of the virus, but now the city of Huanggang will join it in a few hours.

• To catch up on the current state of things, you can read our main news story
• Or read about about what the coronovirus is, and whether we should be worried
• And how, exactly, do you quarantine a city?

Stay with us as we cover the latest updates on the story.