Tech giants' software anonymizes smartphone data to help health agencies monitor COVID-19 spread.

In a few weeks, your smartphone may tell you that you've been close to someone infected by the coronavirus and that you may need to isolate yourself.

By mid-May, Apple and Google will offer a mobile software tool that will let iPhones and Android devices talk to each other and allow digital contact tracing, which tracks those with infections and alerts others who have been in close contact.

Apple and Google will release an API, or application programming interface, that helps a smartphone anonymously detect when it's been near the smartphone of someone who has reported they have the virus.

That API will let software developers build apps — distributed by public health authorities — that could alert users to potential exposures to COVID-19.

Digital contact tracing doesn't diagnose infections; it only tells users if they've encountered someone who is infected. While other companies are building contact tracing apps, the Apple/Google partnership could greatly expand tracing, since:

In the U.S., about 81% of us own smartphones, according to a 2019 survey by the Pew Research Center.  Of those, IDC estimates Android has 86% market share while iOS devices have 14%.

After the Apple/Google API is part of health department apps, the program will be ready for use. Phase 1, described below, involves downloading an app; in Phase II, with implementation yet to be determined, the tech will be part of iOS and Android devices.

How digital contact tracing works

1) Smartphone users voluntarily download a health department app with API from the internet. The apps will be supported on iOS devices introduced within the last four years, and Androids with Android 6.0, introduced in 2015.

2) The downloaded app uses the phone’s Bluetooth Low Energy beacon, which uses short-range radio waves to broadcast an anonymous, random code to nearby portable devices equipped with the same app. To preserve anonymity, the codes change every 10 to 20 minutes.

3) The Bluetooth Low Energy range of most smartphones is about 30 feet. The range can be less if the phone is inside a jacket pocket or purse. When users are mingling in public for five minutes or more, their devices automatically exchange codes and store them for 14 days, the length of the coronavirus incubation period. Distance between phones is calculated on signal strength. Codes are deleted after that.

4) If users learn they have COVID-19, they can voluntarily decide to alert other users with the health authority app. The health authority verifies their diagnoses and sends their codes, called diagnosis keys, to a cloud-based database.

5) Once a day, the database sends a list of diagnosis keys to phones. Keys are analyzed to see if they match any codes collected during the past 14 days. Physical locations and phone owners are not identified.

6) If a match is found, the local public health authority uses its app to alert users that they've been exposed to the virus and advises them how to proceed.

Why digital contact tracing is used

Public health authorities have used contact tracing for years. Tracers interview infected people, learn who they've been in contact with, and advise them on what to do.

Digital versions give contact tracing extra muscle by increasing its reach and speed. Detailed tracking of COVID-19 numbers has spurred hopes of more quickly lifting social restrictions – and tamping down a new outbreak once constraints are eased.

Contact tracing is "a key strategy for preventing further spread of COVID-19," according to the Centers for Disease Control and Prevention.

It's a labor-intensive process, complicated by the lack of trained personnel. Politico reported health departments had less than 2,000 before the coronavirus reached the U.S. Now, as many as 300,000 tracers are needed, a former CDC director told STAT.

But the rapid spread of COVID-19 means traditional tracing methods can be too slow. Even with the best of reporting, data accuracy depends on the memory of those being interviewed, which can be incomplete.

Since the app collects and uploads information automatically, digital contact tracing proponents say it will be faster and more efficient. A report in Science estimates apps could "replace a week's worth of manual contact tracing with instantaneous signals."

Other nations are already using similar digital technology, with varying degrees of severity. Singapore introduced Trace Together in March and China has ordered its citizens to use a Quick Response code on their smartphones. That program rates users' infection risk and decides where they are permitted to travel.

Will contact tracing apps work?

Use of apps is voluntary and the effectiveness depends on the number of people downloading them, how they use them, and how they follow through. That means:

Carrying their phones with them; Keeping their phones active during their daily routines; Using the app to anonymously let other users know if they become infected; Agreeing to follow health department protocols after receiving an infection alert.

Researchers at the University of Oxford say a minimum number of users must be committed to app use. Using simulations based on United Kingdom cities, researchers calculated that 56% of the UK's population would need to use the app, for it to be effective in curbing the pandemic.

However, "even with lower numbers of app users, we still estimate a reduction in the number of coronavirus cases and deaths," the April 16 report said.

What about privacy?

The need for widespread digital contact tracing has raised concerns over possible invasion of privacy, including identification and location, and loss of personal medical information.

In a March 19 letter to the U.S. Office of Science and Technology Policy, Sen. Edward Markey, D-Mass., urged policymakers to "balance privacy with any data-driven solutions to the current public health crisis."

In a similar vein, the Center for American Progress released recommendations for digital tracing while the European Commission recommended a list of anti-theft checks and balances for all tracking apps used against the pandemic.

Both Google and Apple say they've taken precautions to anonymize tracking data. Google says access is granted only to public health authorities whose apps have to meet standards for privacy, security and data control. Those who test positive are not identified to other users or Google or Apple.

Apple told USA TODAY that use is strictly voluntary, locations aren't collected, and that the system is used only for exposure notification and isn't monetized.

The broadcast system can be disabled on a regional basis after it's no longer needed, or users can simply turn them off by uninstalling the tracing application.

The companies say health department apps will be reviewed before being connected. Apple said it's offered to work with regional health departments to strengthen security of their apps.

SOURCE USA TODAY reporting and research; Apple; Google; newscientist.com; University of Oxford; Pew Research Center; Science; Centers for Disease Control and Prevention; STAT

SEARCHABLE MAP: Coronavirus death rates and cases for every US county: https://interactives.courier-journal.com/projects/cv19/map/ 

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