You'll be hearing the word "lockdown" more and more today, and presumably over the coming days too.

A lockdown is not a curfew - as far as we can see, people in affected cities are free to leave home and travel around their city. But the authorities are trying to prevent people getting into these cities, and to stop people getting out, in case infections are spread.

They're doing this by stopping some or all transport to and from these cities - and in some cases they're also suspending public gatherings.

Image source, AFP/Getty Images

Lockdown measures are in place (or are about to be in place) in five cities in Hubei province that are home to many millions of people.

Wuhan's public transport lockdown came into force as of 10:00 local time (02:00 GMT), leaving normally busy train stations and airports empty.

Health authorities are reported to have made wearing a mask mandatory in the city. They are advising people to avoid crowds and public gatherings.

Also in Hubei province:

• Huanggang: The city east of Wuhan announced a suspension of bus and rail systems from midnight, and encouraged people not to leave the city. Cafes, cinemas, theatres and exhibitions in cities have been shut;
• Ezhou, just south of Huanggang, has shut its train stations;
• Xiantao is banning vehicles from entering the Hubei Expressway, is suspending ferries and buses, and says all major events are cancelled;
• Chibi is suspending transport, AFP reports

BBC Technology

An app that tasks users with spreading a deadly virus around the world has skyrocketed in popularity in China amid the coronavirus outbreak.

On Wednesday, eight years after its release, the game became the bestselling app in China.

Some players have suggested people were downloading the game as a way to cope with fears surrounding the virus.

Image source, Getty Images

Developed by UK-based Ndemic Creations, the strategy game, Plague Inc, puts the user in control of a disease they must develop into a global pandemic before the scientific community can develop a cure.

The overall aim is to "bring about the end of human history".

A doctor at a Wuhan hospital has told BBC News of her alarm at the spread of the outbreak. We have chosen to protect the doctor's identity.

"In the last two weeks, there has been an alarming rate of spread," she said. "I am scared because this is a new virus and the figures are alarming.

"The hospitals have been flooding with patients, there are thousands, I haven't seen so many before.

"They have to wait for hours before they see a doctor - you can imagine their panic.

"It's a new virus, so there isn't much information."

China’s National Health Commission has reported an increasing number of cases of the coronavirus that had no exposure to the live food market in Wuhan where the virus is believed to have originated.

Cases without confirmed exposure to the market had been detected overseas, the commission added.

This comes as India confirms one of its citizens in Saudi Arabia has come down with the virus.

• Two Chinese nationals in Vietnam have tested positive for the coronavirus and are being treated in hospital, officials said
• A Chinese man in Ho Chi Minh City was infected by his father who had travelled to Vietnam from Wuhan on 13 January. The father was hospitalised on 17 January. Both have been quarantined and doctors say their fever has abated
• India's foreign ministry says an Indian nurse working in Saudi Arabia had tested positive for the virus - the nurse may have caught the virus while treating a colleague from the Philippines
• Singapore has also confirmed one case of the virus and the health ministry said preliminary tests on another person had come back positive
• There have also been cases in Thailand, Macau, Hong Kong, the US, Taiwan, South Korea and Japan

James Gallagher
Health and science correspondent, BBC News

The honest answer is we don’t really know.

In less than a week, we’ve gone from 40-odd cases to more than 500. But this is hugely misleading as it is the result of the Chinese authorities massively increasing the amount of testing. So they are finding the cases that are already out there rather than detecting “new” infections.

Another challenge is we don’t know when a coronavirus patient becomes infectious to other people. Flu can spread from person to person before symptoms even appear and that allows it to spread incredibly rapidly. Other viruses become infectious only once the disease is more advanced and that slows the pace of an outbreak.

Manya Koetse is editor of What's on Weibo - reporting on the trending stuff from China's largest social network.

Obviously, the coronavirus is a massive topic right now - and Manya is sharing some of the more unusual items doing the rounds on the Weibo social platform.

The total number of cases of the virus in China is now 634, Reuters news agency said, quoting Chinese state television. The death toll, however, remains at 17.

The number of known cases is increasing - up from 500 or so in the last report.

Image source, Getty Images

AFP news agency reports that Beijing's Forbidden City is to close as part of the effort to stop the spread of the virus.

The "city" is actually a palace complex, about 600 years old, which once served as the home to Chinese emperors and the centre of power.

Today, it is a major tourist attraction with millions of visitors every year.

Kerry Allen
BBC Monitoring, Chinese Media Analyst

Beyond travel problems, Wuhan’s lockdown has resulted in disruptions to China’s film and postal industries.

China Post has confirmed that parcels passing through the city are now being subject to a screening and disinfection process. As it is common in China for couriers to deliver goods directly to people via motorbikes, the company is urging consumers to now contact couriers by phone, external, and arrange for their goods to be delivered to a collection point or parcel box "to reduce person-to-person contact".

This means that people stranded in the city may not even receive New Year presents from their loved ones.

At least seven films have suddenly postponed their releases nationwide as well, with Sina Entertainment saying that they’re “worried about the further spread of the epidemic” and “considering the risk of disease transmission in the confined space of cinemas, external”.

This is a major blow to China's film industry - film companies have traditionally tried to schedule their films during Chinese New Year to maximise their profits, given it is the time of year when there are few people are at work.

James Gallagher
Health and science correspondent, BBC News

Yes - large populations of people living in close proximity to animals.

This coronavirus almost certainly came from an animal source, with one suggestion being snakes. Sars, another coronavirus that originated in China, came from bats and the civet cat.

The early cases of this new infection were traced to the South China Seafood Wholesale Market. Live wild animals were also sold including chickens, bats and snakes.

It is a far cry from the usual shopping experience if you are used to your meat nicely cut up and in clear plastic packaging in your typical Western supermarket.

This virus is new, and has been given the temporary name "2019-nCoV" - the n standing for "novel", and "CoV" indicating it's a type of coronavirus.

It causes severe acute respiratory infection - with a fever and a cough - and requires hospital admission, according to the World Health Organisation's guidance, external.

A fever is the main symptom, with some cases involving difficulty breathing. Once checked in hospital, the lungs might show signs of "pneumonic infiltrates".

Of the 17 people known to have died, most were over 60 years old, and several had pre-existing conditions.

Singapore has confirmed its first case of the Wuhan virus, local media report.

The Straits Times reports that a 66-year-old Chinese national tested positive for the virus, quoting a briefing from the health ministry. The man's son is also being treated as a suspected case, it said.

Another woman from China - but who travelled separately - has also been diagnosed with the virus in preliminary tests, which have yet to be confirmed.

Kerry Allen
BBC Monitoring, Chinese Media Analyst

Face mask sales have skyrocketed across China, with the China Daily newspaper noting , externalthat “the surge in demand has hollowed out face mask inventories of some vendors on e-commerce platforms, including Taobao and JD, two of the largest online marketplaces”.

Government mouthpiece People’s Daily has been heavily promoting particular masks people should buy, and which ones should be avoided, external. But it has also been issuing stern warnings against companies seeking to capitalise on the crisis by hiking prices on these products, and says that online vendors will be banned if they are caught doing so, external. (We've written more on that here)

Image source, Hunan TV

Face masks have become the dominant image associated with the city of Wuhan as it goes into lockdown, to the extent that several Hunan provincial TV presenters have worn masks in their bulletins.

Social media users are also seeing reporters based in Wuhan interviewing disgruntled travellers at train stations who have found out their journeys have been cancelled. It’s a rare sight to see someone not wearing a mask in the populous city.

China's state railway group says passengers can get free refunds for rail tickets nationwide from 24 January amid the coronavirus outbreak, state media report.

Hundreds of millions of rail journeys are expected to be made across the country for Chinese New Year, which begins on 25 January.

Rail travel in and out of Wuhan has been suspended and similar measures are due to be applied to nearby Huanggang at midnight local time (16:00 GMT).

James Gallagher
Health and science correspondent, BBC News

There is no evidence this is a risk. Some diseases - including the coronavirus that causes Sars - can spread through surfaces contaminated by people coughing or sneezing on them.

It has not been shown this new coronavirus can do that. Even if it could, there would still be questions about whether international shipping would be a major problem.

Cold viruses tend to survive less than 24 hours outside the human body although norovirus (a severe stomach bug) can last months outside the body.

The most reassuring fact so far is that cases seem to require close contact with another person - say, a family member or healthcare worker - in order to spread.

Image source, Reuters

• The death toll has risen to 17, with 500 cases of the virus confirmed. All the victims were in mainland China
• Wuhan's public transport lockdown came into force as of 10:00 local time (02:00 GMT), leaving normally busy train stations and airports empty
• In Huanggang - east of Wuhan - authorities announced a suspension of the city's bus and rail system from midnight, and encouraged people not to leave the city. The nearby city of Ezhou said it would close its train stations

The information from China is coming thick and fast - here's the best of our material for you to follow:

• Your questions about the outbreak answered
• How worried should we be?
• The city now in lockdown - Wuhan profiled
• How do you quarantine a city - and does it work?
• Full coverage here