What is contact tracing and how will it fight the spread of coronavirus?

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Contact tracing has become an important tool for public health officials in the fight against the spread of COVID-19, and organizations around the world are now creating services designed to warn individuals if they’ve recently come in contact with someone who’s tested positive for the coronavirus. 

The goal of contact tracing is straightforward: to build a list of people who have come within close range of an infected person and use that information to keep exposed people isolated so they don’t transmit the disease to others. Many of these tools rely on  something you already know: your phone’s Bluetooth technology.

For example, Apple and Google announced they are teaming up to make it easier for these health organizations to roll out their broad-range contact tracing. But contact tracing also raises a darker issue — concerns over privacy and security.

Here’s what to know contact tracing and how it will be used in the US and around the world to help slow the spread of coronavirus. This story will be updated often to reflect new information as the situation develops in response to COVID-19.

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What is contact tracing?

Contact tracing is a long-accepted tool used by public health officials to identify individuals who may have come in close proximity with someone who’s tested positive for any disease — not just COVID-19. 

Done the old school way, health officials interview an infected person to build a list of everyone the person in question has seen or spoken to, and where they’ve been while contagious. The officials then reach out to everyone on the list to tell them they’ve been exposed, what steps to take if they have symptoms and how to not infect others.

To combat this particular coronavirus pandemic, our phones have the potential to do this tedious contact-tracing legwork for us, and keep a running list of other phones that come within Bluetooth-tracking range, less than six feet away from you. 

If a person becomes infected, health officials can notify those they came in close proximity with while contagious with advice on how to monitor symptoms, care for themselves and prevent the spread of the virus.

What phones have to do with contact tracing

Taking a written history is laborious and time-consuming. Using the Bluetooth technology already found in your phone allows for a much faster response rate. Here’s how it will work: A phone will use a public-health app in tandem with Bluetooth to broadcast to nearby phones a unique identifier and listen for unique identifiers from other phones with the health app installed. 

For a simplistic example, when we pass each other in the store, my phone’s identifier might be 123456, while yours could be 654321. Each phone will keep a rolling 14-day list of other phones it’s been near.  Using a code prevents someone from gaming the system to report a false infection. To ensure the system isn’t alerting you about inconsequential contacts — such as someone driving by in a car — your phone will only record unique identifiers that are within a few feet of you for a certain period of time, like 10 or 15 minutes.

Then, if someone tests positive, the doctor or lab that administered the test provides a code to enter into the public health app. That code triggers the app to upload to a public health server the person’s unique identifier. The server then alerts everyone who’s been within a few feet of the infected person that they need to self-isolate at the very least, or perhaps get tested for the coronavirus themselves. 

Isolating individuals who may have acquired the virus is especially important because many are asymptomatic but can still transmit the disease to others, who can then develop life-threatening symptoms and even die.

How Apple and Google are teaming up

Using our phones for contact tracing will be most effective if a broad majority of us take part. Oxford University estimates that 60% of a population needs to use phones for tracing to stop a pandemic, although lower adoption numbers will slow the spread.

Between the two companies, Apple and Google have nearly 100 percent of the worldwide mobile phone market — which would potentially offer the broadest platform for digital contact tracing. Because of that, the two tech giants said they will work together to build Bluetooth-based contact tracing into their phones and help public health agencies tap into those capabilities to build their own contact-tracing apps.

Apple and Google won’t build the apps. Instead, they’ll provide the tools that let the health agencies build apps that into the shared foundation across iPhone and Android. The two companies said they expect to have the first tools ready for health agencies in May and plan to expand the tools over the coming months to allow for broader participation. 

Contact tracing is already used around the world

Countries including the UK, Singapore, Australia and others across Europe have either already built contact-tracing apps or have them in the works. 

Israel rolled out a similar monitoring system in March and said the mandatory system would be in place for 30 days.

Will using the contact tracing apps be mandatory?

Israel’s monitoring program is (temporarily) required, but Apple and Google are urging US officials to make the contact-tracing system voluntary, with participants opting into the service, following guidance from the ACLU. 

Contact tracing’s privacy implications

For contact tracing on our phones to be effective, a majority of us need to collect and then potentially share with our local governments a list of everyone we’ve been near for 14 days. But for those already troubled about the loss of individual privacy and the misuse of personal data by tech companies, giving public agencies access to even more personal information raises concerns about how responsible the agencies will be with the data.

Apple and Google said they’re building in safeguards to protect privacy. Contact logs stored on the phone won’t contain personally identifying information: If you’re notified, you’ll know you’ve been in contact with someone sick, but you won’t know who. And to prevent you from being tracked by location, the randomly generated unique identifier your phone broadcasts will change every 15 minutes. The service will be available only to public health officials. 

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Both companies have said they’ll shut down the service once the pandemic ends. Apple and Google, along with public health officials, hope that is enough to convince a skeptical population to widely install and use contact-tracing apps.

Contact-tracing apps are one way to keep tabs on the coronavirus’s patterns and movements before we get a viable vaccine. For more on how to check the spread of coronavirus, here’s what you need to know about COVID-19 testing. Also learn how to protect yourself, how herd immunity can help and how to make your own face mask.