Coronavirus app: What contact tracing is, and how it will work

The UK government has announced that it is soon to release a new contact-tracing app to stop the spread of the coronavirus. This is what we know so far.
Written by Daphne Leprince-Ringuet, Contributor

The UK government is developing an app that will trace back and warn people who have been in contact with someone who is showing symptoms of the coronavirus COVID-19 virus, announced health secretary Matt Hancock at a press briefing. The digital innovation unit of the National Health Service, NHSX, has been working on the new contact-tracing app, which uses smartphone data to prevent the spread of the virus.

The platform will let users register their status in the app if they are experiencing symptoms of the coronavirus. In the case of self-diagnosis, a yellow alert will be sent to any other user who has been in contact with the person experiencing symptoms for an extended period of time. If a user has tested positive for the virus, a red alert will be sent out to indicate that other users should go into quarantine. 

Medical tests confirming that the patient has the virus will come with a verification code that users will have to enter in the app to avoid red alerts being generated unnecessarily.

With traditional public health contact-tracing methods unable to keep up with the pace of the pandemic, the UK government has been looking into the option of tracing smartphones instead for a number of weeks now. 

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A team of medical researchers from the University of Oxford recently modelled a mobile app concept for NHSX, which uses Bluetooth to register all the smartphones (and, therefore, humans) that a given phone has come into close proximity with over a few days. If someone becomes infected, all the users that have signed up to the app can be alerted instantly and anonymously, and advised to go home and self-isolate.

Other countries, like Singapore, are already using mobile apps that tap Bluetooth signals to facilitate contact tracing should users contract the coronavirus. 

Although Hancock did not provide much detail on the app that NHSX is currently developing, he said that the new service is already being tested. "We're already testing this app, and as we do this we're working closely with the world-leading tech companies and renowned experts in clinical safety and digital ethics, so that we can get this right," he said.

A few days earlier, Apple and Google had announced that they are working together to enable the use of Bluetooth technology to help governments and health agencies reduce the spread of the virus. The two tech giants said that in May they will release APIs that will let Bluetooth-based contact-tracing apps run efficiently on both iPhones and Android phones. 

In the model used by Apple and Google, Bluetooth signals would let two users exchange their respective anonymous key codes whenever they come into prolonged contact. If one of the users tests positive for COVID-19, they can register their status in the app, and their anonymous key code will be sent to a central database. The second person's phone, as it downloads the central database, will be able to check for matching key codes, and send a warning when the device recognizes the code of the user who has been infected. 

Bluetooth has been put forward as a solution because, unlike GPS or Wi-Fi data, the technology only tracks which devices have been near one another, instead of registering users' locations. Apple and Google effectively said that user privacy and security had been "central to the design" of their joint effort.

A recent report by Privacy International similarly concluded that Bluetooth is a far less intrusive tracking method than alternatives like GPS or cell-tower data, because it is based on tracking proximity rather than actual location. 

"All data will be handled according to the highest ethical and security standards, and would only be used for NHS care and research," said Hancock in relation to NHSX app. "And we won't hold it any longer than is needed."

Some experts have still voiced concerns about privacy, and are cautious of endorsing an app, even one that limits tracking to Bluetooth signals. Privacy International, for example, mentioned the possibility of de-anonymizing "vast swaths of the population" thanks to Bluetooth data. 

Ross Anderson, professor of security engineering at the University of Cambridge, who is one of a group of people being consulted by the NHS on the privacy and security of contact-tracing apps, equally expressed uneasiness at the prospect of collecting lightly-anonymized data in a system integrated into the government's response to the pandemic. 

"I recognize the overwhelming force of the public-health arguments for a centralised system," he said, "but I also have 25 years' experience of the NHS being incompetent at developing systems and repeatedly breaking their privacy promises when they do manage to collect some data of value to somebody else."

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Privacy is not the only potential shortcoming of Bluetooth technology; according to Anderson, there is also the problem of over-reporting some interactions between individuals, which are not necessarily problematic forms of contact. Bluetooth, indeed, doesn't differentiate between a conversation in the park between two people standing less than two meters apart, and standing behind another shopper at a safe distance in the supermarket queue. 

There is also the issue of false reports. From people tying their phone to their dog and letting it run around a park, to children pranking the service with fake diagnosis, a voluntary app operated by anonymous users risks turning into a playground for trolls of all kinds.

Another issue is that there could be a low uptake of the app. The Big Data Institute estimates that over 60% of the UK population would have to be using the app for digital tracing to reach enough people as they become infected; but based on other examples across the world, reaching that proportion won't be an easy task. In Singapore, for instance, only a fraction of the population (about 13%) has downloaded the contact-tracing app. 

Apple and Google's proposal might offer a solution to this end: the tech companies' ultimate goal is to eventually get rid of the need to download an app altogether, and instead to integrate Bluetooth-based contact tracing directly into their platforms. "This is a more robust solution than an API and would allow more individuals to participate, if they choose to opt in," said Apple. 

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