As the death toll from the new coronavirus climbs, questions remain about how it spread to humans and how much of a threat it poses across the world.

Cases have been confirmed in the US, Japan, South Korea and Thailand, while there are understood to be nine suspected cases being tested in the UK.

Now, fears are growing that the increased travel expected over the upcoming Lunar New Year period could aid the spread.

But just how worried should we be in the UK?

What is it?

A type of virus. As a group, coronaviruses are common across the world, say Public Health England.

Typical symptoms of coronavirus include fever and a cough that may progress to a severe pneumonia causing shortness of breath and breathing difficulties.

Generally, coronavirus can cause more severe symptoms in people with weakened immune systems, older people, and those with long term conditions like diabetes, cancer and chronic lung disease.

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How does this compare with previous outbreaks?

Several experts say the new coronavirus appears to be less severe than its predecessors.

Paul Hunter, professor in medicine at the University of East Anglia, said typical flu epidemics can kill tens of thousands of people, but that previous new coronavirus outbreaks have led to fewer deaths.

For example, severe acute respiratory syndrome (Sars) killed about 800 people, while Middle East respiratory syndrome (Mers) led to about 450 deaths.

Prof Hunter said: “This new strain seems to be rather less lethal than the previous two outbreaks, however this could still change.

“All new outbreaks are worrying, especially in the early weeks when it is not clear how the outbreak could progress.

“I think it unlikely that the Wuhan coronavirus will cause a major public health issue in the UK, in large part because of our existing health system.”

US researchers writing in the journal JAMA also said the fatality rate appears to be lower than that of Sars or Mers.

Catharine Paules and colleagues wrote: “The extent, if any, to which such transmission might lead to a sustained epidemic remains an open and critical question.”

How easily can it be transmitted?

The World Health Organisation (WHO) said on Thursday it was “too early” to declare a public health emergency of international concern.

The body said there is evidence of transmission between people in close contact, such as families or those in health care settings.

But it said it has not seen any evidence of onward transmission.

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Dr Andrew Freedman, reader in infectious diseases at Cardiff University, said it is not clear how contagious the virus is.

He said: “This is important in determining the risk of a much larger outbreak developing, with spread to people who have not travelled to Wuhan.

“It is likely that the US and other countries will be considering what further measures are needed to limit the risk of more cases arriving from China.”

What is the risk to the UK?

England’s chief medical officer, Professor Chris Whitty, has revised the risk to the UK population from very low to low.

Health Secretary Matt Hancock said the UK is one of the first countries to develop a test for coronavirus and the NHS is ready to respond to any cases.

He added: “The public can be assured that the whole of the UK is always well prepared for these type of outbreaks and we will remain vigilant and keep our response under constant review in light of emerging scientific evidence.”

The Foreign Office has advised against all but essential travel to Wuhan, but has not changed its advice on other destinations which have reported cases.

Could cases be confirmed in the UK?

Nine people in the UK are awaiting test results for coronavirus, as the medical director of Public Health England (PHE) said it was “highly likely” cases would be seen in Britain.

Professor Paul Cosford, emeritus medical director at PHE, said it is still “early days” in the course of the virus, but stressed that most of those affected abroad are making a good recovery.

But he said it was “highly likely” that cases would be seen in the UK.

A handful of cases have been identified abroad, including in Japan and the US.

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Officials from Public Health England have been monitoring direct flights from Wuhan city to the UK.

Professor Neil Ferguson, director of the Medical Research Centre for Global Infectious Disease Analysis, said the UK is not a major destination of visitors travelling out of Wuhan.

But, he said: “Border screening and in this case, in the UK, alerting the health system, is not 100% foolproof – there could be a mild case.”

In addition, the screening will only catch people already showing symptoms.

What is the current risk level to the UK?

Public Health England say the risk to the UK population has been assessed as low.

This has been raised from very low due to current evidence on the ability for the virus to spread between people.

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What's being done to protect the UK?

GPs have been told to isolate anyone with symptoms that could indicate coronavirus who have recently travelled from Wuhan in China.

Guidance from Public Health England said doctors should check the travel history of patients.

If they suspect a patient has coronavirus, they should be placed in a room away from other patients and staff with the door closed.

They should not be allowed to use communal toilet facilities or be physically examined, the guidance adds.

A letter from the chief medical officer to clinical staff warns that the "mass movement" of people within and outside China associated with the upcoming Chinese new year celebrations may "amplify transmission".

The letter said that anyone who is confirmed as having the virus will be transferred to a Airborne High Consequences Infectious Disease centre (HCID).

According to Public Health England, there are four interim Airborne HCID centres in England.

These are Guy's and St Thomas' NHS Foundation Trust, Royal Free London NHS Foundation Trust, Royal Liverpool and Broadgreen University Hospitals NHS Trust and Newcastle upon Tyne Hospitals NHS Foundation Trust.

Downing Street said that the Cobra meeting is being chaired by Health Secretary Matt Hancock.

A No 10 spokesman said the UK was "well-prepared" to deal with any new diseases, with medical experts on hand at all airports, while information was being provided to passengers returning from China.