The public will be instructed to stay at home for 14 days, and keep children out of school, even if they have previously had coronavirus or self-isolated, under a new test-and-trace strategy for England to be rolled out on Thursday.
The strategy, which is designed to help end lockdown, will rely on the willingness of people to comply with instructions to self-isolate if they have been close to anybody with Covid-19, health advisers said.
Experts from Public Health England (PHE), who have designed and will oversee the new system, say most people will be willing to stop work and self-isolate, even if they are prevented from earning a living. But ministers have the power to levy fines at a later stage if they feel it to be necessary.
Coronavirus tests will be available to anyone with symptoms. Contacts of those who test positive will be told not to go out, socialise or send their children to school for two weeks.
But they will not be given a test themselves unless they develop symptoms – and even those who have already tested positive for the virus or for antibodies that show they had it in the past will not be exempted from self-isolation.
PHE believes compliance will be good, pointing out that they were able to trace and isolate 95% of contacts of cases before testing and tracing was abandoned on 12 March.
That confidence runs counter to the experience of a group of retired doctors and former public health directors in Sheffield, who reported that up to half contacts, including people working on low wages in care homes, were unwilling or unable to pass on contact details or to stop work because they would lose money or their employer would not approve their absence.
The system, involving 25,000 call handlers working from their homes, is launching ahead of the much-discussed app, which is still being trialled on the Isle of Wight.
The call handlers will first contact anyone who has tested positive and ask for the names and phone numbers of family, friends and colleagues who have been within 2 metres for more than 15 minutes within the previous two days. They will then call those people and instruct them to self-isolate for 14 days.
R, or the ‘effective reproduction number’, is a way of rating a disease’s ability to spread. It’s the average number of people on to whom one infected person will pass the virus. For an R of anything above 1, an epidemic will grow exponentially. Anything below 1 and an outbreak will fizzle out – eventually.
At the start of the coronavirus pandemic, the estimated R for coronavirus was between 2 and 3 – higher than the value for seasonal flu, but lower than for measles. That means each person would pass it on to between two and three people on average, before either recovering or dying, and each of those people would pass it on to a further two to three others, causing the total number of cases to snowball over time.
The reproduction number is not fixed, though. It depends on the biology of the virus; people’s behaviour, such as social distancing; and a population’s immunity. A country may see regional variations in its R number, depending on local factors like population density and transport patterns.
Hannah Devlin Science correspondent
Everyone who experiences symptoms of coronavirus infection will now be able to get a test, said Prof John Newton of PHE, tasked by the government with ramping up testing, which is the essential first element of the new strategy – though their contacts will not get tests. Those contacts will be told that, if they develop symptoms, they should book a test at nhs.uk/coronavirus or by calling 119.
The government believes that any spikes in infections will happen locally, rather than across the entire country, and can be snuffed out with rigorous testing, contact tracing and isolation in each particular town or region.
“As we move to the next stage of our fight against coronavirus, we will be able to replace national lockdowns with individual isolation and, if necessary, local action where there are outbreaks,” said Matt Hancock, the health and social care secretary.
“NHS test and trace will be vital to stopping the spread of the virus. It is how we will be able to protect our friends and family from infection, and protect our NHS. This new system will help us keep this virus under control while carefully and safely lifting the lockdown nationally.”
Some people may believe they are immune, because they have had a positive test in the past. But they will not be exempt from self-isolation if they have been at close-quarters with someone who develops Covid-19.
That decision is partly a judgment on the tests that are available. The swab tests are known to get it wrong in up to 29% of cases, while a positive antibody test is no proof that somebody cannot get the virus again.
“The evidence at the moment is very incomplete. We can’t be certain that people are not infectious. They will still have to self-isolate for 14 days,” said Newton.