Plane passengers have been warned they could be infected with coronavirus thanks to a British businessman who it is feared has already passed it on to at least seven others.
The unnamed 'super spreader' has forced health authorities into a series of emergency tests of hundreds of people.
It comes after the man visited the UK and France from Singapore.
He apparently contracted the virus in the Asian country and fellow passengers on an EasyJet flight to London Gatwick are just some of the scores of people being tracked down who he may have come into contact with.
The authorities are desperate to prevent the spread of the deadly virus, which has already killed over 900 people since December, and are in a race against time after the globe-trotting man fell ill on his return to the UK.
Pressure has been put on Public Health England to reveal exactly where the middle-aged man went and the full extent of the amount of people under observation, reports the Daily Mail.
From East Sussex, he took a four-day trip to the French Alps on his way home from a business trip to Singapore before boarding a flight back to the UK with 183 other passengers and six crew on January 28.
The man id believed to have contracted the virus during a conference last month.
He then prolonged his trip abroad by traveling to a ski chalet in January.
He has been receiving treatment since last Thursday, having already reportedly passed the virus to five other Britons who were staying at the chalet.
While hundreds of villagers are undergoing tests, with the spot a prime location for thousands of visiting skiers this time of year.
As a result of the breakout, tourists have cancelled bookings, according to shop owners.
The chalet's owner, as well as Bob Saynor, an environmental consultant, and his son, aged nine, have all caught the virus off the businessman and are in hospital with three other Britons also from the chalet.
48-year-old Mr Saynor's two other kids and four further Brits from a different family are in quarantine at French hospitals as a precautionary measure.
The Saynors have been living in the village for three months, it is understood. Mr Saynor's wife Catriona, a doctor, is thought to be in the UK, having left France prior to the investigation starting.
She is reportedly under observation in a British hospital, but it is not yet clear if she is the fourth diagnosed case in the country.
A 95-pupil primary school attended by the Saynors' infected son has been closed, as has a 200-pupil school in nearby Saint-Gervais he visited for one day.
Mayor of Les Contamines-Montjoie has confirmed the chalet has been disinfected.
On Sunday, an Easyjet spokesman said it the airline had contacted all of the passengers and crew on the businessman's flight from Geneva to London Gatwick.
The businessman also stopped off at The Grenadier pub in Hove for a couple of hours on February 1, with five staff members ordered to self-isolate, as was a school pupil.
The conference he attended in Singapore saw 94 other business people come together, with participants from Malaysia, South Korea and Britain also diagnosed with coronavirus.
China has raised the death toll to 811, passing the number killed globally by the SARS epidemic.
While more than 900 have died worldwide and 37,000 have been infected, with the epicentre, Wuhan, the sprawling capital of Central China’s Hubei province, in lockdown.
Experts including Dr Nathalie MacDermott, from King's College London and Professor Richard Tedder, a visiting professor at Imperial College London, have expressed concerns of the epidemic turning into a pandemic.
It is believed the outbreak may have started in one of the Wuhan's popular wet markets.
More than 100 UK nationals were put in quarantine at Kents Hill Park hotel in Milton Keynes on Saturday following the last of a series of evacuation flights from the Chinese city.
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