Schools and businesses are closing and experts are warning of widespread lockdowns as the threat of a coronavirus outbreak hits the UK.
The medical director of Public Health England says that the UK government would "take actions to isolate more widely" if the virus spreads and refused to rule out the possibility that entire towns would be shut down to prevent an outbreak.
Speaking on Radio 4, Professor Paul Cosford said: "I think you have to be cautious about the idea of closing down communities, towns, and so on.
"But what will happen is when we see - if we do get to the position of a more widespread infection - we will monitor that as it develops.
"We will take the best scientific advice to how we may be able to delay transmission further and if that includes actions to isolate more widely then of course we will do that.
"But I think at the moment this is unlikely."
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Cosford's comments come as a leaked report suggest that up to 500,000 could die from the virus in the UK if it infects up to 80 per cent of the population.
The scenario was described as a "reasonable worst case" in the briefing to ministers, which was leaked to the Sun newspaper.
Schools across the country have closed because of the risk posed by staff and pupils who have travelled overseas during the half-term break.
Many of those schools had organised skiing trips to northern Italy, where the virus is spreading quickly and the death toll has reached 12.
Businesses are affected too, with 300 staff at oil giant Chevron's London office sent home after a staff member displayed flu-like symptoms after returning from a country where there have been confirmed cases.
Staff will work from home "for the time being", pending tests on the employee.
Countries outside China, the source of the outbreak, are being warned that they are "simply not read" for coronavirus.
Dr Bruce Aylward, the WHO's China envoy, warned: "Time is everything in this disease. Days make a difference with a disease like this."
He added that the world is "simply not ready".
"It can get ready very fast, but the big shift has to be in the mindset."
More new cases of the disease have been reported outside China than inside for the first time.
On Tuesday, 411 new cases of the Covid-19 disease were reported in China, while 427 were reported outside the country, the World Health Organisation (WHO) said.
"Yesterday, the number of new cases reported outside China exceeded the number of new cases in China for the first time," WHO chief Tedros Adhanom Ghebreyesus told diplomats in Geneva.
Countries across the world are now scrambling to prevent the spread of the virus, which was first detected at a seafood market in Wuhan in December.
In the past three months, more than 80,000 people have been infected across 40 countries, while more than 270 have died.
The latest countries to be hit included Algeria, Austria, Croatia, Greece and Switzerland on Wednesday.
South Korea announced more than 1000 infections – by far the largest outside China – and 12 deaths, while Italy, the hardest hit country in Europe, had more than 370 cases and 12 deaths.
Iran announced a total of 19 deaths and 139 infections, including the country's deputy health minister.
As yet, New Zealand has no confirmed cases.
IS IT A PANDEMIC YET?
Around the world cleaning crews scrubbed down everything from money to buses and military bases and hotels were on high alert for the disease.
Worries about the economic impact are growing with factories idle and tourism crippled.
The dramatic surge of infections in Italy, Iran and South Korea has prompted calls for the virus to be declared a pandemic.
The WHO defines a pandemic as a situation where "the whole world's population" is likely to be exposed to an infection and potentially "fall sick".
The declaration would prompt countries to step up their preparedness plans, but the WHO said it could also cause unnecessary panic.
"We should not be too eager to declare a pandemic," Tedros said on Wednesday, stressing that such a declaration could "signal that we can no longer contain the virus, which is not true".
"We are in a fight that can be won if we do the right things."
But Tedros insisted the WHO would not hesitate to declare a pandemic if it was "an accurate description of the situation".
"I am not downplaying the seriousness of the situation, or the potential for this to become a pandemic, because it has that potential," he said.
"All countries, whether they have cases or not, must prepare for a potential."
-Additional reporting, News.com.au