Britain on Monday said the number of confirmed coronavirus cases had doubled to eight as the government declared the virus a serious and imminent threat, giving it additional powers to isolate those suspected of being infected.

British nationals who have been flown back from Wuhan are being quarantined for 14 days while travelers returning home from other Asian countries have been told to self-isolate if they showed any of the coronavirus symptoms. The new cases in Britain are linked to a Briton who had returned from Singapore and stayed at a French ski resort between Jan. 24 and 28.

On Sunday, French health officials said five British nationals including a child had been diagnosed with the new coronavirus at the mountain village.

Airline easyJet said Public Health England had contacted all passengers who were on board a flight from Geneva to London on Jan. 28 after one of those on board was later diagnosed with coronavirus. The airline said “Although the risk to others on board the flight is very low, crew who operated the flight have been advised to monitor their health for a 14 day period since the flight in line with Public Health England advice.