Mass testing will cut how many people will need to be quarantined by the track and trace system
Mass coronavirus testing will cut down the sheer numbers who will need to be quarantined under coronavirus contact tracing, a study has found.
Contact tracing, still in the process of being set up in the UK, involves identifying anyone who has been in close proximity to a Covid-19 case and telling them to self-isolate to curb the potential spread of the virus.
The Government has yet to clarify if people who are tracked will be given a test during their quarantine period. Therefore, they may have to stick out a 14-day period ‘just in case’ they have the virus.
Researchers have predicted hundreds of thousands of Brits will be thrown into self-isolation every day as a result, which could wreak havoc on their daily life – after already spending months in lockdown.
A team led by University of East Anglia simulated a pandemic with almost 470 people in the village of Haslemere, in Surrey, using phone data to determine movements and social circles.
They built an interactive platform where the public can see how the virus spreads in a town by selecting different scenarios – including how many people don’t show symptoms.
Across all of the simulations used, an average of 12 per cent of the population – up to a high of 15 per cent – end up infected, if the virus is left to spread uncontrollably over 70 days.
With contact tracing, nine per cent of the population would be infected. But 12 per cent of people identified would need to be quarantined at the most severe point of the outbreak in order to curb the spread.
If a high number of tests were available to Haslemere’s residents – reaching one in ten people – quarantined cases would be slashed to 1.7 per cent at the peak – and even less over the entire outbreak, leaving people to carry on with their normal lives.
To reach the same effect in Britain, 6.66million tests would be needed every day. But currently testing capacity in the UK is hovering around a mere 100,000.
On top of that, the roll out of contact tracing has been embroiled in chaos. The contact tracing system, involving an army of 25,000 phone handlers and an NHS phone app, was promised to be up and running by June 1, when schools will re-open ahead of other rules being relaxed in mid-June, but progress has stalled.
A team led by University of East Anglia simulated a pandemic with almost 470 people in the village Haslemere, in Surrey, using phone data to understand people’s movements and social circles. Across all simulations used, an average of 12 per cent of the population end up infected if the virus is left to spread uncontrollably over 70 days. With contact tracing, 12 per cent of people identified would need to be quarantined at the most severe point of the outbreak in order to curb the spread
If a high number of tests were available to Haslemere’s residents – reaching one in ten people – quarantined cases would be slashed to 1.7 per cent at the peak – and even less over the entire outbreak
The team assessed how the huge numbers of people that would need to be quarantined as a result of contact could be avoided under different scenarios
The researchers from University of East Anglia, Oxford University and the London School of Hygiene & Tropical Medicine re-purposed data collected for the BBC Four Pandemic experiment (in 2017).
Some 1,272 people downloaded an app which followed their movements. It gauged how many people the average individual comes into contact with at their home, work and other settings.
It helps to understand exactly how a disease spreads among a community, in this case, Covid-19, which has killed at least 46,000 people in Britain.
The researchers honed in on 468 people who had sufficient phone data over three days, showing everyone they had come within one metre of for face-to-face conversations.
They worked out a ‘Haslemere social network’ and, using mathematical models, investigated how quickly SARS-CoV-2 would spread over the course of 70 days once one person was infected.
The journey of the outbreak can be seen on their interactive website, where a user can change the infection and intervention settings themselves.
The simulation showed if symptomatic people isolated – as is the current UK Government guidance – an estimated 9.3 per cent of the population would end up infected, compared to 12 per cent if nothing was done.
Contact tracing reduced it to 9 per cent but social distancing and testing people as individual measures failed to make much difference to the outbreak.
Lead researcher Dr Lewis Spurgin, from UEA’s School of Biological Sciences, said: ‘Our epidemic model showed that uncontrolled outbreaks typically resulted a significant proportion of the population becoming infected.
‘We found contact tracing reduces outbreak size, but can result in lots and lots of people getting quarantined as the outbreak grows.’
The researchers combined outbreak control measures to show how effective they would be in tandem. These were displayed in illustrations.
Researchers worked out a ‘Haslemere social network’ (the blue lines represent one social contact between two people). Using mathematical models, investigated how quickly transmission of SARS-CoV-2 would happen over a 70-day outbreak once one person (the red dot) was infected
This is an example of how one case leads to several more without any control (left, B). But quarantining at-risk people through contact tracing (represented by the grey boxes), it reduces the spread of the virus
This simulation shows how social distancing (cutting the number of blue lines) slows the spread of the virus as well as limiting how many people go into quarantine
Huge numbers of people are expected to need quarantining as a result of contact tracing – but the study showed this could be avoided.
Without any testing at all, 50 people (12 per cent of the population) would need to be quarantined per week in the Haslemere scenario.
By ramping up testing capacity to 50 tests every day, reaching ten per cent of people, and therefore testing and releasing more quarantined cases, less than 10 people would need to be quarantined in the worst week – about 2.5 weeks in.
Over the course of the outbreak, only 1.7 per cent of people would need to quarantine because a negative test result would free swathes of people.
However, a huge number of tests would have to be available if contact tracing was to be this effective in the UK.
With just five tests per day in Haslemere, covering one per cent of the population, around 25 people would need to be quarantined every day during the peak of the outbreak.
Social distancing had two benefits – it had a ‘marked reduction’ in the number of quarantined cases by 1.2 per cent, and slashed how many tests were needed.
Dr Adam Kucharski, from the London School of Hygiene and Tropical Medicine, said: ‘An important finding of our study was that moderate social distancing, combined with contact tracing and testing, could help control the spread of Covid-19 while reducing the number of people who need to be in quarantine.’
Even though this is a comprehensive study to predict how the UK’s outbreak will play out, it is likely to be different in the real world.
Models such as these rely on a lot of assumptions, including how much transmission is a result of asymptomatic spread, how long it takes for a person to show symptoms and how successful contact tracing is.
Due to the rapid response nature of this research, it has not yet been peer-reviewed.
But it provides valuable insight into potential ways to contain the pandemic using data from real-world social interactions – something which has not been done in such detail until now.
Dr Spurgin said: ‘We wanted to find out how contact tracing can be best used to stop the spread of Covid-19 – not least because more disruptive interventions, such as lockdowns, cannot be sustained for a long period of time.’
Dr Josh Firth, of the University of Oxford and joint-lead author of the study, said: ‘Human social behaviour is obviously very complex, so it is important that we are able to see how people socialise and interact in real life, rather than relying entirely on simulations of social interactions within communities.
‘Going forward, real-world networks will be an important tool for considering epidemic spread, and our study provides new evidence into how contact tracing and social distancing strategies could potentially be combined to control Covid-19 outbreaks within local populations.
‘It is important to note the limitations of this study and the current state of knowledge – particularly that the social network here is taken from within a single, small town, and therefore larger-scale tracking efforts will be needed if we want to extrapolate these approaches to larger cities.’
A recent paper by from the London School of Hygiene & Tropical Medicine, led by Dr Kucharski, attempted to estimate how many people nationwide would need to quarantine when contact tracing comes into place.
Estimates were based on the effects of manual contact tracing or the use of an app – both of which the government plans to use. But the team did not look at the effects of both methods combined, which would likely overlap.
They projected for every 5,000 new cases in the UK every day, 68,000 people could be asked to quarantine themselves each day if officials relied solely on a tracing app. But this dropped to just 54,000 people under the same scenario, if Brits were limited to seeing a maximum of four people each day to contain the outbreak.
Under a regime using only an army of volunteers to manually trace the spread of the virus, the figure was as high as 190,000 people a day, or 140,000 with a limit on the size of social gatherings.
When the same model was applied to 20,000 new cases a day, it suggested up to 770,000 people may be asked to self-isolate each day through manual tracing, or 580,000 if Brits are told to stick to seeing only four people each day.
While the figure was in the region of 220,000-270,000 under the same scenario for the app.
The coronavirus is still infecting 61,000 people per week in England, according to data published by the Office for National Statistics on May 21. The true figure could be as high as 111,000 people every seven days or as low as 29,000, the data shows – and experts say the rate of infection is ‘relatively stable’.
The Government will launch a widespread contact tracing scheme to track down people who have been in touch with infected patients
Contact tracing will also involve the NHSX app, which alerts people who have been in close contact with those who report having symptoms of COVID-19
How many people will need to self isolate when contact tracing is in place? A recent study from the London School of Hygiene and Tropical Medicine (LSHTM) estimate that for every 5,000 new cases in the UK every day, 190,000 people would be told to self isolate by contact tracers. It goes up to 770,000 for every 20,000 new cases. With just app-based tracing, the number of people that would need to self isolate reduces because an app doesn’t identify as many people
Ministers are set to combine different interventions – testing, social distancing, and contact tracing – in order to keep on top of the virus and avoid a second deadly wave.
Contact tracing is being implemented worldwide because it health health chiefs stay one step ahead of the virus.
It has been a key part of the response in several Asian countries that have successfully reduced case numbers, but has not been used in the same way in the UK.
Contact tracing was used right at the start of the outbreak in the UK when they were only a handful of cases and Public Health England could somewhat identify anyone those infected people had been in contact with.
But as the outbreak began to spiral out of control, the method was ditched because cases were too difficult to keep up with. That’s where the lockdown came into effect.
As part of its plan to prevent a second coronavirus wave, officials have recruited 25,000 contact tracers as part of what they say will be the largest virtual call centre operation in the country. These workers will pinpoint those who need to quarantine with old-fashioned interviews on diagnosed cases.
Boris Johnson announced in parliament that these ‘manual contact tracers’ will be employed, trained and ready to track 10,000 new cases of the virus a day by 1 June – when the UK moves into phase two of the easing the lockdown.
There is skepticism this system will not be ready in time before hundreds of pupils and their teachers return to schools up and down the UK, giving a feeling of unease.
Health Secretary Matt Hancock said the contact tracing smartphone app, made by NHSX, would be rolled out by the middle of May after a pilot study on the Isle of Wight.
But this has now been pushed back for ‘several weeks’, officials have said, meaning it’s possible it won’t play a part in the contact tracing scheme before the lockdown is loosened further next Monday.
The app alerts people who have been in close contact with those who report having symptoms of COVID-19, such as a cough or fever. Those people are then asked to self isolate, although ministers haven’t revealed for how long.
NHS Confederation chief executive Niall Dixon has warned of ‘severe consequences’ if the government’s test, track and trace system isn’t in place soon, saying that easing lockdown before it is available would risk a second wave of infections that could overwhelm hospitals.
In a letter to Health Secretary Matt Hancock, Dixon welcomed the news of the contact tracer recruitment but added that ‘health leaders are yet to see detail on the strategy that underpins this’ – referring to what sort of questions employers will ask people with the virus and how they will ask for phone contacts to be supplied.
‘This is about saving lives and protecting the NHS, Dr Dixon said. ‘If we do not set up the right system, involving local agencies, we will put patients and NHS staff at risk.’
The recent LSHTM study predicted the success of different pandemic control measure, finding the call-handler contact tracers could reduce transmission by 61 per cent.
That’s based on the assumption that 95 per cent of all people at school and work would be successfully contact traced and told to isolate.
The team estimated that with app-based tracing, spread would drop by 44 per cent – under the condition half of the public had the app on their phone.
The pilot study of the NHS app on the Isle of Wight saw just 35 to 40 per cent of residents install the app, but the researchers said they think it would be higher nationwide based on survey results.
In both situations, new cases could be limited even further if some social distancing remained in place and individuals had an inner circle of only four people. It would also slash how many people would need to self isolate as a result of contact tracing by thousands.
HOW WILL CONTACT TRACING WORK?
Contact tracing is seen as one of several possible remedies to help the UK out of lockdown and an app trial is now ready to go. Here’s out it will work:
What is contact tracing?
Contact tracing is a way of tracking social networks around people so that when one of them gets diagnosed with COVID-19 the rest of them can be alerted that they might be at risk.
This is intended to stop people passing on the virus without realising they might be infectious.
The British Government is working on an army of 18,000 human contact tracers who will question COVID-19 patients, as well as the app which will log connections in the background.
Why is the trial being done on the Isle of Wight?
The app is being trialled on the Isle of Wight because it is a small, self-contained community which is easier to control, Mr Hancock said.
He claimed it could be tested in ‘proper scientifically-controlled conditions’ there because people cannot come and go freely – there is no bridge or tunnel between the Isle and mainland Britain.
It will be easier for officials to get a clear idea of what proportion of the population has downloaded the app, and to get tests for large parts of communities quickly.
How will the app work?
Once installed and set up, the app will run in the background, keeping a log of everyone you pass.
Users will need to provide the first part of their postcode and give the app permission to use Bluetooth, as well as its ability to receive notifications.
Bluetooth will need to be kept on.
When a person is feeling unwell, they need to send a report, stating whether they are experiencing a high temperature and a continuous cough, and when these symptoms started. If it appears they might have the virus, the person will be told to book a test.
The information is then uploaded, along with the last 28 days of proximity events, and fed into a complex at-risk algorithm which crunches data such as distance, duration and symptoms.
It will only notify those deemed at risk to isolate for 14 days and ask them monitor their symptoms.
If the person’s results come back as negative, those who came into contact with them will be told they are able to come out of isolation.
But should the result be positive, the person will be told to self-isolate for seven days, while those who came into contact with them continue self-isolating and book a test of their own if they have slightest symptom.
What will constitute close enough contact for someone to be warned?
The Department of Health said a ‘complex risk algorithm’ will be used to dictate who has been in close enough contact for them to be warned. It is not clear how this is calculated.
The World Health Organization’s rule is someone is at risk if they have spent 15 minutes within six-and-a-half feet (2m), but the level of contact may change this. For example, physical contact is likely to require less exposure time than car-sharing to produce the same risk.
Will the contract tracing app be effective and when will the rest of the UK get it?
The app was first tested on staff at RAF Leeming, and air base in North Yorkshire, where trials ‘went well’. Contact tracing is really dependent on several crucial factors – though NHSX boss Matthew Gould has warned it will not be a ‘silver bullet’.
‘The app is exciting, but it’s also not a silver bullet or a standalone solution, it’s part of this wider strategy… it has to be seen as part of this strategy alongside the expansion of testing and human contact tracing,’ he said.
The app is also voluntary, so its effectiveness will rely on the amount of people actually using it.
If it proves to be usable and uptake is good in the Isle of Wight trial, it is expected to roll out to the rest of the UK in mid-May, the Department of Health said.
What if people don’t record when they develop a cough?
The app will rely on people being honest about when they think they have symptoms of the coronavirus, and what their test result is. These must be logged on the app by the user because the NHS will not link the app to patient records or even to someone’s name. People who are dishonest about their health risk putting others at risk of COVID-19.
Source: Press Association