Health officials are urgently trying to track down anyone who came into contact with the first two people in the UK confirmed to have the coronavirus.
The pair – who are members of the same family – had been staying at the StayCity apartment-hotel in York when they became unwell, Public Health England (PHE) has said.
It is understood they recently travelled to the UK from China.
On Wednesday night, the building – which has been thoroughly disinfected – was put on lockdown when some family members, believed to be Chinese nationals, were taken to hospital after falling ill.
Professor Chris Whitty, chief medical officer for England, said: “We can confirm that two patients in England, who are members of the same family, have tested positive for coronavirus.
“The patients are receiving specialist NHS care, and we are using tried and tested infection control procedures to prevent further spread of the virus.”
He said they were being treated at a specialist infectious diseases unit at the Royal Victoria Infirmary in Newcastle.
The risk to the public has been upgraded from “low” to “moderate”, said PHE.
Professor Sharon Peacock, director of the National Infection Service at PHE, said people who had come into contact with the two confirmed cases were being traced.
She said they did not know how many people that might be.
“Close contacts will be given health advice about symptoms and emergency contact details to use if they become unwell in the 14 days after contact with the confirmed cases,” she said.
“This tried-and-tested method will ensure we are able to minimise any risk to them and the wider public.”
The PHE definition of close contact is being within two metres of the infected person for 15 minutes.
Of the 177 tests in the UK, only two have been positive.
Prof Whitty said the two cases do not increase the risk to the UK and the virus remains “moderately transmissible”.
It currently has a 2% mortality rate – considerably lower than the outbreaks of Ebola (70%) and SARS (10%).
Coronavirus: Masks ‘going for £125’ as demand grows in Hong Kong
He said the NHS is “extremely well-prepared” with “robust infection control measures in place to respond immediately”.
“Nevertheless, if we got very large numbers that is obviously a concern and this would be something we would have to take very seriously,” added Prof Whitty.
The Newcastle upon Tyne Hospitals’ NHS Foundation Trust said other patients and visitors at the hospital where the two people are being treated should not be worried and attend appointments as usual.
Coronavirus: Briton ‘very relieved’ after last-minute dash to make flight out of Wuhan
An evacuation flight carrying 83 Britons from Wuhan – the epicentre of the outbreak – arrived at Brize Norton RAF base in Oxfordshire at around 1.30pm on Friday.
An image from inside the plane, which also had 27 foreign nationals on board, appeared to show empty seats – suggesting not all those the government had anticipated evacuating had made the flight.
Deputy chief medical officer Dr Jenny Harries said everyone on the plane was a “well passenger”.
She said all of them had thermographic screening and were subject to ongoing questioning and assessment during the journey.
Cabinet Office minister Michael Gove told Sky News that Britain would send another plane if necessary.
The Britons were taken on a convoy of coaches to Arrowe Park Hospital on the Wirral, Merseyside, where a special facility has been set up for them to be quarantined for 14 days.
While in quarantine, the evacuated Britons are being given fully furnished rooms, food, laundry facilities and have access to a team of medical staff.
Kitchens are also available and families are being kept together, with games consoles, toys and cots provided.
What is a global health emergency?
The World Health Organisation declared the outbreak a global health emergency on Thursday and said the spread of the virus outside China was a key factor behind its decision.
Its director-general, Tedros Adhanom Ghebreyesus, said: “This is the time for facts, not fear. This is time for science, not rumours. This is the time for solidarity, not stigma.”
A total of 213 people have been killed by the virus in China where there have been more than 9,800 cases reported, as authorities around the world work to prevent a global pandemic.
There is no vaccine for the new viral infection, which can cause pneumonia and can be passed from person to person.
The symptoms include fever, coughing and difficulty breathing.
Though the origin of the virus has yet to be identified, the WHO has said the primary source is probably an animal.
The virus originated in the Chinese central city of Wuhan at the end of last year and has since spread to every province across mainland China.
How far has the coronavirus spread?
A total of 98 cases have been found in another 21 countries including the US – which has advised against all travel to China – Taiwan, South Korea, Russia, Japan, Thailand, France, Australia, Germany, Singapore and the United Arab Emirates.
Airports around the world have stepped up screening of travellers arriving from affected regions.
Measures are also in force in the UK to guard against the virus, including taking aircraft to a special designated area of Heathrow’s Terminal 4.
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