Britons who are aged over 70 or those with underlying health conditions have been advised not to go on cruises by Prime Minister Boris Johnson.

The UK government has also banned overseas school trips from Friday.

But chief scientific advisor Patrick Vallance appeared to suggest flights would not be grounded.

UpdateCruise lines respond to Foreign Office cruise ship advice

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He said the government looked at stopping flights from China but added: “Unless you can stop 95% (of all flights) the effect on delay of the transmission is just a day or two.”

He added: “It really wasn’t going to make a big difference.”

Vallance also ruled out screening at airports, saying the first person to be confirmed with the virus in the US had gone through screening but had not been diagnosed.

The new measures were announced on Thursday afternoon after the government held an emergency Cobra meeting.

Those with a new persistent cough or high temperature have been advised to self-isolate for seven days.

Johnson said it was “the worst public health crisis for a generation” and estimated up to 10,000 people in the UK could be infected but not diagnosed.

There are so far 596 confirmed cases across the country.

The government said it was moving towards a “delay phase” to lower the peak impact of the virus.

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