If the government wants to start lifting restrictions, it needs to find a way to identify and rapidly isolate people with new symptoms © FT Montage/Dreamstime

The UK wants to emulate the success of countries such as South Korea and Germany in rolling out a mass programme of contact tracing to limit the spread of coronavirus when lockdown restrictions are eased.

Matt Hancock, health secretary, has said a “large-scale” operation will be up and running within weeks to identify people who are newly infected and rapidly warn those they have come into contact with that they could be at risk. The government is now recruiting a tracing army of 18,000 people, including council workers and public health staff, and developing a smartphone app to map potential contacts.

The theory is that since lockdown measures have reduced the infection rate, it will be easier to keep track of emerging cases. “The fewer new cases, the more effective test, track and trace are as a way of keeping the disease down, and therefore more of the social distancing measures can be lifted,” Mr Hancock told MPs last week.

However, Jeremy Hunt, the former health secretary, has warned that the logistical challenge of getting the new system up and running “shouldn’t be underestimated”. “This is bigger than building the Nightingale [hospitals] or PPE distribution,” he said.

What is contact tracing?

Traditional contact tracing, carried out by public health officials, is a painstaking process likened to detective work. Tracers interview a patient, identify anyone who has had close contact with them and attempt to alert these people as soon as possible. Contacts considered to be particularly high-risk are intensively monitored for any sign that they have become infected.

Tedros Adhanom Ghebreyesus, director-general of the World Health Organization, said early in the coronavirus outbreak that “tracing every contact must be the backbone of the response in every country”. South Korea has been particularly successful in using this method to keep coronavirus deaths low, at 243, despite having more than 10,000 cases. The UK has reported more than 154,000 cases and over 20,000 deaths.

Diagram explaining how Apple and Google’s joint proposal for a contact tracing system could work

Public Health England conducted contact tracing for six weeks between January and March, alerting almost 4,000 people that they had a risk of infection on the back of about 590 positive cases. However, the agency stopped the scheme on March 12, arguing that it was no longer effective because community transmission was so widespread. Some public health experts have suggested that while this might have been the case in hotspots such as London, continued tracing could have helped control the outbreak in the 50 health authorities that had fewer than 10 cases at the time tracing was halted.

Why is the UK starting up again now?

Lockdown measures have suppressed the growth in the number of UK cases. But if the government wants to start lifting restrictions, it needs to find a way to identify and rapidly isolate people with new symptoms, and others they may have unwittingly infected. One senior public health doctor told the Financial Times that contact tracing would be “essential” for containing the virus during the next 12-18 months, until there is a vaccine or treatment.

“If we are to switch from 80 to 90 per cent of the population being locked down to perhaps 10 to 20 per cent . . . at any one time, we need to know who needs to be quarantined and isolated,” the doctor said.

Ministers are pursuing a dual-track approach: boosting the number of human contact tracers working for Public Health England from 290 to about 18,000; and developing an app that will allow members of the public to request a testing kit and automatically alert others they have come into contact with that they may also be infected. Human tracers are needed to work alongside the app because the experience in Singapore — whose contact-tracing app has been downloaded by only 17 per cent of the population — shows that wide take-up is not guaranteed.

Will it work this time?

The definition of success is simple, according to Mr Hunt. Can anyone with symptoms get a test in 24 hours? And can 80 to 90 per cent of their contacts be traced in the following 24 hours?

The promise of the app is that it will offer immediate communication with potential contacts. NHSX, the digital innovation arm of the NHS, is working on a platform that would allow users to input their symptoms. This will instantly trigger alerts to be sent to other people whose phones have been near the infected person’s phone during the likely transmission window.

Singapore’s contact-tracing app has only been downloaded by 17% of the population, showing wide take-up is not guaranteed © AFP via Getty Images

Speed is important because analysis by Oxford university has found that half of all transmissions in China occurred before anyone showed symptoms. Oxford researchers have also found that delaying contact-tracing by even a day after symptoms appear could make the difference between controlling the epidemic and allowing a second wave of infections.

The problem with apps is persuading enough people to use them. It is estimated that a minimum of 60 per cent of the population need to download the app for it to be effective. Ipsos Mori polling commissioned by the FT indicated that at least two-thirds of Britons were prepared to let the government use smartphones for contact tracing.

The other important element, as Mr Hunt points out, is testing. The government is racing to reach its target of testing 100,000 people a day by the end of this week. This capacity is critical because people with symptoms need confirmation of whether they have coronavirus to update their contacts on the level of risk. And negative tests will prevent large networks of people who have been in contact with a symptomatic person from being in quarantine unnecessarily.

What does this app mean for privacy?

NHSX is developing a Bluetooth-based tracing app that exchanges signals between nearby phones. Currently in trials, this logs interactions without disclosing users’ names and numbers. Apple and Google are working on their own Bluetooth tracing system, which, they say, has a high privacy standard and prevents governments storing any data centrally. NHSX says it has been in touch with Apple and Google but has not yet confirmed whether it will be using the template offered by these tech companies.

Other tracing methods, such as apps using geolocation data, are more intrusive. But one industry expert warned that any app that cannot track people’s physical movements will be unable to identify potential infection hotspots. “They have chosen not to track people’s physical locations, even though it's a cornerstone of the guidelines from the WHO,” the expert said. “The model for this app also delegates the responsibility to citizens and assumes that everyone takes part.”

The problem is that while an app using location data may be more useful to governments, it is considerably less private. At the extreme end of public health policy, South Korea’s contact tracing system used footage from surveillance cameras and credit card transactions to plot the movements of confirmed virus sufferers.

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