Europe has been hit by a second wave of coronavirus, Health Secretary Matt Hancock has warned, saying cases are "rising sharply" in some countries on the continent.
Mr Hancock said the UK government was "prepared to take action, sometimes quite quickly" in order to prevent the wave coming to the UK.
He suggested more countries could follow Spain in being removed from the UK's list of safe destinations, saying "we're prepared to take that action to keep people here safe".
The deputy chief medical officer for England, Professor Jonathan Van-Tam, announced the change in advice on Thursday.
He said the change was being made due to the “low but real possibility of infectiousness” between seven and 10 days after the onset of the illness.
Mr Hancock explained the policy shift, saying the scientific advice is "constantly" updating "and when the scientific changes...then we are guided by that science".
"When the facts change then of course we update our policy," he added.
He said the government was taking a "precautionary approach" in order to avoid being part of the second wave he says has hit continental Europe.
Advice for those who have been in close contact with someone with the virus remains unchanged.
Health Secretary Hancock told ITV News his "critical message" to anyone with symptoms was to "get a test - it's so important that people do - and then follow the medical advice".
It came as NHS Test and Trace launched a campaign to encourage anyone with symptoms to get a test for free.
Chief Executive Chair of NHS Test and Trace, Dido Harding said: "I urge everybody to get a free test as soon as you experience coronavirus symptoms and to follow the advice you’re given if you are contacted by the service. If we all continue to play our part, then together we can stop the spread of this virus.”
Guidance from the NHS also said that people must self-isolate for 14 days if you live with, or are in a bubble with, someone that has symptoms.
Those who are contacted by NHS Test and Trace must also quarantine for 14 days.
Mr Hancock also hinted that ministers are working on ways to reduce the current quarantine period for new arrivals to the UK from 14 days, amid pressure from the tourism industry.
“We’re always looking at how we can have the least possible burden of the measures that we have to put into place so that is something on which we’re doing some work but we’ll only come forward with a proposal when we’re confident that it is safe to do so,” he told Sky News.
It is not yet clear whether the self-isolation period for people with symptoms, which was introduced in March, will also be increased in Scotland, Wales and Northern Ireland.