By Q Radio news
The period of self isolation for those who test positive for Covid-19 is to increase from seven to ten days.
It follows fears of a second wave of the pandemic in parts of Europe.
All four Chief Medical officers in the UK took the decision in a bid to try to curb a resurgence of the disease.
If somebody has symptoms of Covid-19 they'll now have to stay at home for ten days, instead of seven.
Scientists now believe there's a "real possibility" people may continue to be infectious for longer than a week.
(The Coronavirus isolation period to be increased from seven to ten days)
The UK's chief medical officers said on Thursday that the period must increase from the current rule of seven days because of the risk individuals may still be able to spread Covid-19.
In a joint statement, they said the change for those who experience the key symptoms of a new continuous cough, high temperature or loss of taste or smell is needed because of the "low but real possibility of infectiousness" up to 10 days.
Their move came as official analysis said England had the highest levels of excess mortality in Europe across the first half of 2020.
Mr Hancock earlier warned that a new spike in Covid-19 cases is "clearly" beginning to emerge in Europe as he said "we've got to do everything" to prevent it reaching the UK.
"I am worried about a second wave. I think you can see a second wave starting to roll across Europe and we've got to do everything we can to prevent it from reaching these shores and to tackle it," Mr Hancock told Sky News.
He said 10-day isolation measure was "part of that, but so, too, are the measures we're taking, for instance, to ensure that we don't directly bring cases back to this country where there's a big spike in cases".
"So, absolutely, on a second wave it is something I worry about and I worry about it because we can see it happening," he added.
The chief medical officers for England, Wales, Scotland and Northern Ireland said that it is "now the correct balance of risk" to extend the isolation period for those who test positive or have symptoms to 10 days.
"Evidence, although still limited, has strengthened and shows that people with Covid-19 who are mildly ill and are recovering have a low but real possibility of infectiousness between seven and nine days after illness onset," they said.
Anyone with symptoms who has a Covid-19 test that comes back negative does not have to continue with the isolation period.
Government sources said the risk of people transmitting the virus seven days after onset of symptoms is pretty low and after 10 days it is even lower.
But they said the move had been made to provide "maximum protection" and to keep UK disease levels as low as possible.
Dr Shaun Fitzgerald, a Royal Academy of Engineering visiting professor at the University of Cambridge, said: "This change is important.
"Given that there is now stronger evidence which shows a real possibility of infectiousness between seven and nine days after illness onset, 10 days' isolation seems very sensible."
Meanwhile, Labour's shadow health secretary Jonathan Ashworth described the Office for National Statistics analysis suggesting England had the worst death rate in Europe as a "devastating moment".
"We can no longer hide from the fact the Government has not handled this crisis well and needs to urgently learn lessons from its mistakes," he added.
The analysis said that by the week ending May 29, the death rate in England was 7.55% higher than the average for the previous five years.
Spain ranked second at 6.65%, followed by Scotland (5.11%), Belgium (3.89%) and Wales (2.78%).
The excess mortality measure is seen as the best way to compare deaths during the crisis because it takes into account not just Covid-19 deaths but those from the indirect impacts of the pandemic, such as delayed access to healthcare.
Mr Hancock also warned travellers that new countries could be added to the quarantine list in the coming days after passengers arriving in the UK from Spain were ordered to isolate for two weeks as cases there increased.
He said ministers are looking at ways to reduce the 14-day period, possibly by the use of multiple tests, amid pressure from the tourism industry.
But he said ministers are constantly considering whether to add countries to the quarantine list and when pressed if new nations could be added in the next few days, he replied: "Yes."
Government data showed the seven-day average of new cases in the UK had increased to just over 700 compared to around 550 in the second week of July.
However, the figure remained far lower than at the start of May when the average was close to 5,000.