Telling those with a high temperature or cough to self-isolate for a week will have the “biggest impact” in the fight against coronavirus, the UK’s chief science adviser says.
Sir Patrick Vallance said the new advice, as the UK moved to the next “delay” phase of tackling the outbreak, was a “big intervention”.
But ex-Health Secretary Jeremy Hunt called for more stringent measures.
Opposition parties asked to see the scientific evidence behind the advice.
On Friday afternoon the government announced that mayoral and local elections in England and Wales have been postponed for a year.
All professional football leagues in England, and professional and grassroots games in Scotland, have been suspended until at least 3 April.
The Six Nations rugby union match between Wales and Scotland on Saturday has also been postponed.
The two other final day games had already been postponed and it is not known when the 2020 Championship will be completed.
The Foreign Office has advised against all but essential travel to some areas of Spain, including Madrid, but flights will continue as normal.
There have been 798 confirmed cases across the UK as of 09:00 GMT on Friday, which is a rise of 208 on the day before.
Health officials have said they believe the actual number of people infected could be between 5,000 and 10,000.
In total, 10 people have now died in the UK with the virus.
Jeremy Hunt told BBC Newsnight the decision to hold off cancelling large gatherings was “surprising and concerning” when we have “four weeks before we get to the stage that Italy is at”.
Much of Italy – the world’s worst-hit country after China – is currently in lockdown as its tally of deaths has topped 1,000.
“You would have thought that every single thing we do in that four weeks would be designed to slow the spread of people catching the virus,” added Mr Hunt, who was health secretary for six years and quit as foreign secretary in July.
In talks on Friday morning, opposition parties – including Labour, the SNP, Plaid Cymru and the Lib Dems – questioned the government’s approach, raising “genuine concerns” that the UK is not taking similar measures to some EU countries.
They said constituents’ questions on social distancing were not being properly addressed – and that people were being left to form their own judgments.
Requests to see evidence of the behavioural science behind the government’s approach were also made.
But Sir Patrick told BBC Radio 4’s Today programme: “The most likely place you are going to get an infection from is a family member or friend in a small space, not in a big space.”
Defending the new tactics, he said: “The first set of measures are actually rather large.”
“We have just asked a lot of people to isolate, stay at home, if they have got symptoms of mild upper respiratory tract infection, cough or fever. That is a big change,” he added.
“We have also talked about the possibility of whole households staying at home if one person has got [coronavirus] – that may come in later.
“And importantly we are also talking about that during the peak when people are most likely to get infected, the elderly and vulnerable are properly protected. This is not a short-term thing, it is going to go on for weeks.”
He said that closing schools was a “very effective way of dealing with pandemic flu” but that with this coronavirus, “the role of children is less clear in terms of spreading the disease”.
Sir Patrick said it is hoped the government’s approach will create a “herd immunity in the UK”.
“Our aim is to try and reduce the peak, broaden the peak, not suppress it completely,” he said.
“Also, because the vast majority of people get a mild illness, to build up some kind of herd immunity so more people are immune to this disease and we reduce the transmission.
“At the same time we protect those who are most vulnerable to it.”
He also said the new coronavirus is likely to become “an annual seasonal infection”.
Why is the UK doing it differently?
Many countries are taking tough measures such as school closures, cancelling mass gatherings and severe travel restrictions. But the UK has adopted relatively modest controls.
The difference can be explained partly by the fact some of countries are further into their epidemics.
Computer simulations indicate the UK is in the early stages. The government’s top scientists believe it is too soon to impose severe restrictions.
Such limitations might last several months and risk “self-isolation fatigue”, with people leaving their homes when the epidemic reaches its height.
Many elderly people, who are particularly at risk of developing severe symptoms, are already isolated. Cutting them off from their communities now, when the risks are still relatively low, would create unnecessary difficulties for them.
School closures have also yet to be announced. Such measures are effective for controlling serious flu epidemics, but Covid-19 seems to affect children less. In addition, school closures would take many much needed NHS staff away from their jobs while they look after their children.
Mr Hunt, chair of the Commons health and social care committee, said countries who appeared to have been successful in turning back the virus had “moved very early” on introducing social distancing.
Sir Patrick said that new advice for care homes would become important as the epidemic progressed.
Prime Minister Boris Johnson’s official spokesperson said 38 planners from the military are being deployed to help local areas draw up plans to provide support to councils and public services.
On Thursday, Mr Johnson announced new measures aimed at protecting the elderly and those most vulnerable to the disease – including that anyone with a persistent cough or high temperature should self-isolate for a week.
The PM said there was no need to close schools at the moment, saying “the scientific advice is that this could do more harm than good at this time”.
The UK government’s health advisers are working on the assumption that Britain will not see infection rates peak for up to three months.
Ministers said it was important to get the timing right for stricter measures because people would tire of them after a few weeks.
As the epidemic reaches its peak, it is likely elderly people and those with health conditions will be told to cut social contact and stay at home.
Scotland is among the countries to have restricted mass gatherings, along with the Irish Republic, which has also closed schools and other public facilities. Schools in Northern Ireland will close at some stage, First Minister Arlene Foster said.
Elsewhere, France is one of the latest European countries to close all schools, universities and nurseries. In the US, all major sport has been suspended and Broadway performances are off for a month.
In other developments:
- School leaders called for clear guidance ahead of any widespread school closures
- Cabinet Minister Anne-Marie Trevelyan tested negative for coronavirus after coming into contact with Nadine Dorries, the first MP to contract the virus
- The Queen has cancelled her public engagements for the rest of March
- Prince Charles and the Duchess of Cornwall have cancelled their trip to Bosnia and Herzegovina, Cyprus and Jordan in the spring
- The University of Oxford said it “intends to remain open until instructed otherwise” after six students test positive
- Saint Patrick’s Day celebrations were cancelled in London
- Some care home firms announced restrictions on visitors, with one banning children from seeing residents
- The Electoral Commission recommended that local polls due in May should be postponed until the autumn
Public Health England has released new guidance for those staying at home because they have symptoms of the virus – a cough or a temperature of 37.8C (100F) or more.
Its advice states:
- Not to go to work, school, or public areas, use public transport or taxis – or even for a walk
- Those with even mild symptoms of infection should stay at least two metres away from other people in their homes, and should sleep alone
- Those with confirmed or suspected cases should use a separate bathroom if they can, or thoroughly clean facilities after using them if they live with other people
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