A British man who caught the new coronavirus in Singapore is feared to be a “super spreader” who is linked to seven other confirmed cases in the UK, France and Spain.
Four more patients in England tested positive for the illness on Monday, bringing the total number of cases in the UK to eight.
The four new cases are all understood to be contacts of the businessman, who was diagnosed in Brighton last week and who contracted the virus at a conference in Singapore.
He was the third confirmed case of the coronavirus in the UK and is understood to be the first British person to have contracted the disease.
On Monday, the UK government introduced new powers to deal with the coronavirus and declared it a “serious and imminent threat to public health”.
Experts have warned that Britain is facing a “major outbreak” of the disease.
It comes as the death toll in China from the virus rose to 908, with the number of confirmed cases in the country reaching 40,171.
Professor Chris Whitty, the chief medical officer for England, said the British patient is "a known contact of a previously confirmed UK case, and the virus was passed on in France".
MailOnline said the patient is a British businessman in his 50s, whose movements prompted testing of hundreds of people on his flights, an Alpine ski trip and a visit to his local pub.
The man travelled back to the UK on an easyJet flight from Geneva in Switzerland on January 28.
An easyJet spokeswoman said: “EasyJet has been notified by the public health authority that a customer who had recently travelled on one of its flights has since been diagnosed with the coronavirus.
“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.
“As the customer was not experiencing any symptoms, the risk to others on board the flight is very low. We remain in contact with the public health authorities and are following their guidance.”
The airline said crew had been advised to monitor themselves for 14 days since the flight and that none of them are displaying any symptoms.
He is thought to have been diagnosed in Brighton and was transferred to St Thomas' Hospital in London, where there is an infectious diseases unit, last Thursday.
Five British nationals who tested positive for coronavirus in France were diagnosed after they came into contact with the British national who had recently returned from Singapore.
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.
French officials said the British national who was in Singapore returned on January 24 and stayed for four days in the area in eastern France, before returning to England on January 28.
A British man in Majorca has also tested positive for coronavirus, while his wife and two daughters tested negative.
According to the government in the Balearic Islands, the family said they had been in contact with a person who tested positive for coronavirus in France.
Professor Paul Hunter, professor in medicine, University of East Anglia, said: "From today's reports, this new case would appear to be linked to the cluster of cases in the French ski resort which is also linked to the case in Brighton.
"As such, this case is part of the same cluster which is being reported as linked to a British national returning from Singapore.
"Whilst we currently do not know many details about how this new case was linked to others in the cluster, his/her identification does not at this stage indicate wider spread within the UK community.
"If the new individual had been already identified through contact tracing and the person was self-isolating then this should not pose any additional risk.”
On Monday, the Department of Health said people with coronavirus can now be forcibly quarantined and will not be free to leave, and can be forcibly sent into isolation if they pose a threat to public health.
A spokesman said: “Our infection control procedures are world leading and the NHS is well prepared to deal with novel coronavirus.
“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.
“This measure will rightly make it easier for health professionals to help keep people safe across the country.”