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(Pocket-lint) - Watch any movie about infectious disease outbreaks, and you'll see one common plot scenario: Scientists and public health experts racing against the clock to find each sick person, including who they've been in contact with most recently. This is called contact tracing, and it continues until every last person who might've been exposed has been found. It's how you help stop the transmission of a virus.

What is contact tracing?

Traditionally, when a person gets sick, they are then interviewed by public health officials and asked about their recent interactions to learn who has been exposed to the virus, such as the novel coronavirus. Officials then contact those people to learn about how they’re currently feeling and to tell them to quarantine. They also learn about who they've contacted, and then those people will be phoned.

It's a painstaking process that, on a global scale, often means there aren't enough resources to trace contacts for every new infection. In many places, experts have just stopped trying to track everyone down. That's where phones come in handy.

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How does contact tracing work in smartphones?

All smartphones use wireless radios to exchange data over long ranges via cell towers or Wi-Fi routers, but phones with Bluetooth chips can support short-range transmissions up to 30 feet away. So, in terms of COVID-19, a Bluetooth phone owner could be alerted within seconds if they've been nearby another Bluetooth phone owner who has been diagnosed with COVID-19.

Both Bluetooth phone owners would simply need to be using an app or a device involved with some sort of contact tracing initiative, and then they'd be able to report their symptoms or diagnosis to that system. Their information could then be instantaneously tracked, possibly heat-mapped, and anonymously relayed between the nearby phone owners over Bluetooth. Easy.

Oxford University estimated that 60 per cent of a population needs to use phones for contact tracing to completely stop a pandemic.

How are Google and Apple helping contact tracing efforts?

Google and Apple announced they're developing a system that will let iPhone and Android phones use Bluetooth data to track if you have been near other people diagnosed with COVID-19, the disease that causes the novel coronavirus. Essentially, if someone tests positive for the virus, they'll be able to tell an app that supports the system, which then notifies the phones of everyone nearby.

In other words, contact tracing is a proven technique, and smartphones could help make it possible on a global scale. It could potentially even be a really effective form of contact tracing. Think about it: You can only name people you've exposed if you personally know them. But, with Google and Apple's system, the stranger you exposed last week can be immediately alerted, if both of you use it.

Google and Apple's system, which you can read more about here, will be to be built into their own phones, and it'll help public health agencies - like the NHSX - tap into those capabilities to build their own contact-tracing apps. Either way, it'll be completely voluntary. Only the necessary information will be collected, and your personally identifiable information will never be given to others.

Apple and Google dominate the worldwide mobile phone market and have the potential to offer the broadest platform for contact tracing. They're planning to offer an API to health agencies in May and hope to grow their system.

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Who else is using smartphones for contact tracing?

Several countries - the UK, Singapore, Israel, Australia, and others in Europe - have built contact-tracing apps or have them in development. In the UK, for instance, the NHSX is working on a contact tracing app that will also work with Apple and Google's incoming system.

Are there any privacy concerns with contact tracing?

Apple and Google's system, and even a proposal from researchers at the Massachusetts Institute of Technology, randomly generates IDs on devices that send Bluetooth signals to other devices with an app installed. If people identify themselves as COVID-19 positive and give consent to share that information, every device that interacts with those IDs in set time will get a notification.

The collected IDs will be deleted every 14 days and are completely separate from any personal information. They're useable only for tracking, too. Google and Apple have released white papers on the cryptography and Bluetooth specifications behind their contact-tracing system.

But, let's be honest: Google and Apple's contact tracing system seems like mass surveillance. It will fail if they can't convince enough people to try it. Due to the tech industry's long history of data scandals, not to mention concerns by privacy watchdogs, we don't blame people if they are wary of Google and Apple's system. Both companies will need to encourage people to trust their system.

Governments can't make their contact-tracing system mandatory, either. Apple and Google said that would violate their conditions. The ACLU has also proposed guidelines to ensure privacy and transparency for contact tracing systems, and it recommends the systems be opt-in. They say no one should force you to use a contact tracing system, whether it's a government agency or school. 

Pew found that 60 per cent of Americans believe location tracking won't make a difference in limiting the spread of COVID-19 spread, but 45 per cent think it's OK to track people who have had contact with an infected person. 

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Writing by Maggie Tillman. Originally published on 22 April 2020.