How Apple and Google plan to check the coronavirus spread with contact tracing

Your phone may soon be able to alert you if you've come in close contact with someone who tested positive for coronavirus.

Clifford Colby Managing Editor
Clifford is a managing editor at CNET, where he leads How-To coverage. He spent a handful of years at Peachpit Press, editing books on everything from the first iPhone to Python. He also worked at a handful of now-dead computer magazines, including MacWEEK and MacUser. Unrelated, he roots for the Oakland A's.
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Clifford Colby
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Contact tracing can help public health officials slow the spread of coronavirus.

Angela Lang/CNET

In the fight against coronavirus, Apple and Google have teamed up to help public health officials build apps to trace the spread of the disease from person to person. The two Silicon Valley giants won't make the apps themselves, however. Instead, they are now providing the tools and resources that health organizations can use to build their own contact tracing apps. Along with antibody testing and nasal swab testing, contact tracing is considered one of cornerstones that health authorities will use to check the spread of COVID-19 and decide how and when to reopen their cities and regions as we wait for a vaccine.

The goal of contact tracing is simple enough: 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. But the work required to do effective tracing is hard, and Google and Apple are involved because modern contact tracing can use your phone and its Bluetooth technology -- something Apple and Google know a lot about -- to monitor who people come in close proximity with.

But contact tracing also brings up a worrying issue -- concerns over privacy and security -- that Google, Apple and health organizations need to overcome for tracing to be effective. 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 the coronavirus and reopen the economy. This story will be updated often to reflect new information as the situation develops in response to COVID-19.

Watch this: Contact tracing explained: How apps can slow the coronavirus

What is contact tracing?

Contact tracing is a long-accepted -- and until recently little-known -- 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.


If someone near you gets sick -- even a stranger -- contact tracing apps would let you know.


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. 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.

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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 are providing the tools that let the health agencies build apps that tie into a shared foundation across iPhone and Android. The two companies just released their initial collection tools that government agencies can use to build their own tracing apps. The companies said 22 countries and a handful of US states -- including Alabama, North Dakota and South Carolina -- have requested access to the tools. The two companies expect to grant access to more states and countries in the coming weeks.

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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 or where. 

The companies said they are scrambling identifying information to ensure people cannot be tracked. And to prevent you from being monitored by location, the randomly generated unique identifier your phone broadcasts will change every 10 to 20 minutes. The service will be available only to public health officials. 

Watch this: Vaccines, antibody tests, treatments: The science of ending the pandemic

Both companies have said they'll shut down the service on a regional basis as 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 the coronavirus, here's what you need to know about COVID-19 testing. Also learn how to protect yourselfhow herd immunity can help and how to make your own face mask.

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