The number of people infected by the coronavirus in the UK has doubled to eight – after four more patients tested positive for the virus.
It comes as the government issued new powers in England to keep people in quarantine to stop the virus spreading.
In order to do this the Department of Health has described the coronavirus as a “serious and imminent threat” to public health.
The overall risk level to the UK remains “moderate”.
There have been more than 40,000 cases of the virus globally, mostly in China. The total number of deaths in China is now 908 – but the number of newly-infected people per day has stabilised.
The new cases are all linked to a British man who caught the virus at a conference in Singapore and stopped at a ski resort in France before returning to the UK. He was diagnosed in Brighton, and is being treated at St Thomas’ Hospital in London.
Confirming the four new cases on Monday, chief medical officer for England Prof Chris Whitty said they were all “known contacts of a previously confirmed UK case, and the virus was passed on in France”.
He added that they have been transferred to specialist NHS centres at Guy’s and St Thomas’ and the Royal Free hospitals in London.
On Monday, the Health Secretary Matt Hancock said he had introduced new regulations in England as “the transmission of coronavirus would constitute a serious threat”.
The BBC’s political correspondent Iain Watson said the measures were announced because a passenger on the first UK flight from Wuhan, who is currently being held in quarantine on the Wirral, “is threatening to abscond”.
“Currently the regulations are not strong enough to stop him leaving before the 14-day period is up so they brought in these new regulations to try and compel him to stay put,” he said.
The Department of Health insisted on Twitter that the latest announcement on the coronavirus threat to the public was “a legal term which we announced this morning as part of changes to make it easier for health professionals to do their job”.
A government spokesman said: “We are strengthening our regulations so we can keep individuals in supported isolation for their own safety and if public health professionals consider they may be at risk of spreading the virus to other members of the public.”
Why have they issued this advice?
Tackling the coronavirus threat has taken the government into uncharted territory. Quarantining hundreds of British citizens for two weeks has never been done on this scale in modern times.
Whitehall sources say the latest Department of Health announcement on the virus threat covers the tightening of some regulations to help enforce quarantine powers.
This gives legal underpinning to the quarantining of people back from Wuhan in Milton Keynes and the Wirral.
They all signed contracts committing to the 14-day isolation but it’s understood that more rigorous regulations are needed to ensure people stay the course.
This is not a ramping up in official warnings to the wider public. The language used in the official release describing an “imminent threat” was over dramatic and confusing and probably there only for obscure legal reasons.
The actual threat level announced by Public Health England a couple of weeks ago remains moderate.
Under the new measures, Arrowe Park Hospital, on the Wirral, and Kents Hill Park conference centre, in Milton Keynes, have been designated as “isolation” facilities in the UK.
Evacuees from Wuhan, where the virus outbreak first emerged, who travelled to the UK on two flights chartered by the Foreign Office are currently in quarantine at the two locations.
On Sunday, around 200 British and foreign nationals arrived on the second and final flight at RAF Brize Norton.
A statement on the Department of Health website said: “The Secretary of State declares that the incidence or transmission of novel coronavirus constitutes a serious and imminent threat to public health, and the measures outlined in these regulations are considered as an effective means of delaying or preventing further transmission of the virus.”
It is estimated that 1% of people infected with the new coronavirus may die, according to a report by the World Health Organization Collaborating Centre for Infectious Disease Modelling.
Prof Neil Ferguson, of Imperial College London, said: “Our estimates – while subject to much uncertainty due to the limited data currently available – suggest that the impact of the unfolding epidemic may be comparable to the major influenza pandemics of the 20th century.”
The five British nationals being treated in France were diagnosed after they came into contact with the British carrier, according to the French health ministry.
The four adults and a nine-year-old child, who are not in a serious condition, were staying in the Alpine resort area of Contamines-Montjoie near Mont Blanc.
EasyJet confirmed that the Briton flew from Geneva back to the UK on 28 January, and health officials are trying to trace other passengers who might be at risk.
A spokeswoman said: “Public Health England is contacting all passengers who were seated in the vicinity of the customer on flight EZS8481 from Geneva to London Gatwick on 28 January, to provide guidance in line with procedures.”
Meanwhile, a British man in Majorca has also been diagnosed with coronavirus, while his wife and two daughters tested negative.
The family said they had been in contact with a person who tested positive for coronavirus in France, the government in the Balearic Islands said.
The new virus was first reported in Wuhan, the capital of Hubei province. The city of 11 million has been in lockdown for weeks.
The outbreak was declared a global emergency by the WHO on 30 January.
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