Chinese President Xi Jinping has held a special government meeting on the Lunar New Year public holiday to warn that the spread of a deadly new virus is “accelerating”.

The country is facing a “grave situation” Mr Xi told senior officials, according to state television.

The coronavirus has killed at least 41 people and infected almost 1,300 since its discovery in the city of Wuhan.

Travel restrictions have already hit several affected cities.

And from Sunday, private vehicles will be banned from the central districts of Wuhan, the source of the outbreak.

A second emergency hospital is to be built there within weeks to handle 1,300 new patients, and will be finished in half a month, state newspaper the People’s Daily said. It is the second such rapid construction project: work on another 1,000-bed hospital has already begun.

Specialist military medical teams have also been flown into Hubei province, where Wuhan is located.

The urgency reflects concern both within China and elsewhere about the spread of the virus which first appeared in December.

• How can China build a hospital so quickly?
• Coronavirus sparks anxiety among Chinese overseas

Lunar New Year celebrations for the year of the rat, which began on Saturday, have been cancelled in many Chinese cities.

Across mainland China, travellers are having their temperatures checked for signs of fever, and train stations have been shut in several cities.

In Hong Kong, the highest level of emergency has been declared and school holidays extended.

Several other nations are each dealing with a handful of cases, with patients being treated in isolation.

What is the coronavirus, and what does it do?

A coronavirus is a family of viruses which include the common cold.

But this virus has never been seen before, so it’s been called 2019-nCov, for “novel coronavirus”.

New viruses can become common in humans after jumping across the species barrier from animals.

The Sars [Severe Acute Respiratory Syndrome] outbreak of 2003 started in bats and transferred to the civet cat which passed it on to humans.

This new virus also causes severe acute respiratory infection.

Symptoms seem to start with a fever, followed by a dry cough and then, after a week, lead to shortness of breath and some patients needing hospital treatment.

There is no specific cure or vaccine.

Coronavirus: How worried should we be?

Based on early information, it is believed that only a quarter of infected cases are “severe”, and the dead are mostly – though not exclusively – older people, some of whom have pre-existing conditions.

What’s happening at the source?

The city of Wuhan is effectively on lockdown, with heavy restrictions on travel in and out, and public transport options from buses to planes cancelled.

It is a major population centre with up to 11 million inhabitants – comparable in size to London.

Pharmacies in the city have begun to run out of supplies and hospitals have been filled with nervous members of the public.

But even for those free of infection, there has been an impact on daily life, as officials have urged people to avoid crowds and gatherings.

“The whole transport system has been shut down,” Kathleen Bell, who is is originally from the UK and works in Wuhan, told the BBC. “From midnight tonight private cars are not allowed on the road. And taxis aren’t running.”

“You have queues of people lining up to be seen, some may not have the virus, and some may, and they’re all in the same space,” she said.

• Wuhan: The London-sized city where the virus began
• How do you quarantine a city – and does it work?

Major Western brands such as McDonald’s and Starbucks have closed in the city and in others nearby.

“The streets are pretty much empty,” said Mustafa Siddiqui, a businessman in Wuhan. “No-one’s going outside.”

“There’s no real panic. There is calm. There is nothing really happening.”

The surrounding Hubei province is also deeply affected, with nearly a dozen cities enduring some sort of travel restriction.

Where has it spread?

There are now nearly 1,300 confirmed cases all across China, though most concentrated in those closest to Hubei.

But it has also spread abroad – in isolated cases affecting small numbers of patients.

On Saturday, Australia confirmed its first four cases – first in Melbourne, and then three more in Sydney.

It has also spread to Europe, with three cases confirmed in France. The UK is investigating a number of suspected cases, with officials trying to trace around 2,000 people who have recently flown to the UK from Hubei province.

• Wuhan woman who ‘cheated’ checks found in France
• Fourteen people in UK tested for new strain

The cases largely involve people who had recently travelled from the affected region in China.

China’s neighbours in the Asia region are on high alert, however, with cases reported in Thailand, Singapore, Japan, Taiwan, Malaysia, Vietnam, South Korea and Nepal.

There are also cases in the United States.

The World Health Organization has not classed the virus as an “international emergency”, partly because of the low number of overseas cases.

What is the impact on new year celebrations?

The Lunar New Year is one of the most important dates in the calendar in China, where millions of people travel home – something that is a problem for preventing the spread of a virus.

Authorities have shut major tourist sites including the Forbidden City in Beijing and a section of the Great Wall, and cancelled major public events in other parts of the country, including:

• Traditional temple fairs in Beijing
• An international carnival in Hong Kong
• Hong Kong’s annual football tournament
• All public Lunar New Year celebrations in Macau

Shanghai’s Disney Resort is temporarily closing.

In the capital, Beijing, and also in Shanghai, officials have asked residents who return from affected areas to stay at home for 14 days to prevent the spread of the virus, local media report.

• China’s travel industry counts cost of coronavirus
• How is China coping with the coronavirus outbreak?

Learn more about the new virus

• Your questions: You asked, we answered
• The story explained: How worried should we be?
• Wuhan profiled: The city now in lockdown
• In detail: Follow all our coverage here

Are you in China? Have you been affected by the lockdown in various cities? Email haveyoursay@bbc.co.uk.

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“Incoming, Incoming!” The loudspeaker screeches out a warning of a rocket attack at Union III, the US-led coalition base in Iraq’s capital, Baghdad.

The compound is in the Green Zone, an area built around what was once former Iraqi leader Saddam Hussein’s palace.

A few seconds after the first alarm, we hear two loud explosions. Then another announcement, ordering everyone in the base to take cover.

Just across the road lies the US embassy, the likely target of the three Katyusha rockets.

After an hour, we are told it is safe enough to come out. One rocket fell into the nearby Tigris river, but two landed inside the embassy compound.

“This isn’t the first and won’t be the last,” says Pari, a 42-year-old civilian, who lives and works at the base as a hairdresser to support her daughters back home in Kyrgyzstan.

She used to work at the US base in the Afghan capital, Kabul, but left because it was too dangerous.

Everyone told her she would have a calmer life in Baghdad, but two rockets hit the street near the embassy on her first night there.

Watershed moment

Since October 2019, more than 109 Katyusha rockets have been launched at locations housing US troops in Iraq.

The coalition says Iran-backed paramilitary groups are carrying out the attacks.

Then came the US killing on 3 January of Gen Qasem Soleimani, the head of Iran’s elite Quds Force at Baghdad airport.

Iran’s response, five days later, was a ballistic missile strike against US bases in Iraq.

These attacks prompted new security rules for all coalition bases housing US troops in Iraq.

Outside activities are now banned and anyone walking in the open has to wear protective gear from sunset until early morning.

During the coalition’s fight against the Islamic State (IS) group, I went on several operations with the US army and travelled to their bases across Iraq.

I was told it was unnecessary to wear body armour inside the compounds. It was safe, I was assured.

But the Union III base in Baghdad is far emptier than the last time I was here.

Many of the coalition forces, including Nato soldiers, have been relocated to Kuwait.

Officials tell me the soldiers will return when the threat level goes down.

Strained relations

But there are bigger and deeper developments being felt by US army officers in Iraq since the attack.

The Union III base is the main headquarters for Iraqi and coalition forces in their campaign against IS.

When I was last here, both the US and Iraqi officers were keen to show the media how their relationship was deepening on a professional and personal level.

Both sides were keen to appear on camera to talk about their mutual goal of defeating IS.

Now, coalition commanders are hesitant to go on the record. Recent developments have cast a long shadow over what was once “a great friendship”.

The deputy head of a pro-Iran paramilitary force, Abu Mahdi al-Muhandis, was also killed in the US strike against Gen Soleimani.

Interestingly, he was in this very base in Baghdad’s Green Zone a couple of days before his death.

His Shia Muslim paramilitary group is supported by Iran, but is also an official part of the Iraqi security forces and has played a key role in the defeat of IS.

He was here to meet Iraqi army generals, the same commanders who are partners with the US in the battle against IS.

Muhandis’s picture can be seen on the wall alongside other Iraqi military commanders in the same corridor that coalition officials would walk through each day if they wanted to see their Iraqi partners at the base.

In the dark

Two senior coalition officials in the Union III compound told me they only found out about the assassination when they checked their phones in the morning.

“If there is an operation that you don’t need to know about, you wouldn’t be told,” a senior coalition official said on condition of anonymity.

“No matter if you have to live with its aftermath.”

• What does international law say about the assassination?
• Voices from Iran: ‘Soleimani did not deserve such a fate’
• Qasem Soleimani: Who was Iran’s ‘rock star’ general?

In fact, the night Soleimani and his convoy were hit, US drone operators working out of the Baghdad base thought at first that there had been a rocket attack on the airport’s diplomatic centre where most of the coalition diplomats and intelligence officers are housed.

It had been targeted only a few days before the assassination.

When they saw the fire after the explosion, they assumed it was a drone strike as rockets would not cause that kind of blaze, but were unsure about who had carried it out.

This happened only a few days after US forces in Iraq carried out air strikes on the headquarters of the Iranian-backed Kataib Hezbollah militia on both sides of the border with Syria; this was in response to rocket attacks on coalition bases and killed at least 25 members of this Iraqi Shia paramilitary group.

Their funeral turned into a big demonstration against the US and mourners attacked the US embassy in Baghdad. But the drone attack crossed all the red lines, according to Shia paramilitary groups.

Angry with moves that had nothing to do with the US mission in Iraq to “defeat IS”, pro-Iran paramilitary groups and politicians want US troops to leave Iraq immediately.

But coalition forces hope to start what they say will be the final stages of operations against IS with their Iraqi allies soon.

It is this uncertainty that makes commanders on both sides reluctant to talk to the media about it, especially when politicians might contradict them the next day.

“Our team is looking forward to and believes in the mission. We believe in the Iraqi people, and we believe in the Iraqi security forces,” a senior coalition official who has been deployed to Iraq multiple times during the campaign against IS and has worked closely with the same top Iraqi commanders tells me.

He used to see his Iraqi counterpart almost every day to drink tea together, but since the attack, their relationship has become more formal.

The Iraqi security forces feel they are trapped in a political crisis between Iran and the US.

“This is not our problem,” says Maj Gen Tahseen al-Khafaji, Iraq’s joint operation command spokesman. “This is not even a military problem. There is a crisis between Iran and the US and they have put us in the middle.

“My message is for both these countries: Don’t bring your issue here.”

The Iraqi military says the pause in coalition support in the wake of Gen Soleimani’s death has left them with no other option but to continue the operation against IS themselves.

“For the first time, we have flown our F-16 jets to conduct air strikes on IS,” says Gen Khafaji.

“It is right that we can fight alone, but we are still looking forward to working with the coalition if political issues allow.”

For the moment, everything hangs in the balance. The nature of the threats US forces face have been shifted from IS to something completely different.

US airman Alejandro Pena, who was despatched to Iraq only two months ago, has the final word on this.

“When we were deployed here, I thought I was coming to fight IS, but after a couple of months I saw that ‘ah no! There are others as well.'”