Californians Can Now Track Covid-19 Exposure on Their Phones
By: Thomas Smith
Tags: Apps, Public Health, Covid 19, Technology

Californians Can Now Track Covid-19 Exposure on Their Phones

CA Notify app installation. Images: Gado Images

California took a major step forward in Covid-19 technology today when the state became among the first in the USA to launch a customized coronavirus exposure notification app. This morning, many Californians awoke to an Android or iOS notification informing them that the app, called CA Notify, was live.

Users can download CA Notify from the Google Play Store on Android or the App Store on iOS devices. It is also being pushed to your phone to prompt you to sign up.

CA Notify uses your phone to track potential Covid-19 exposures as you go about daily life and to notify you of situations where you might have been exposed to a Covid-19 positive person. Because our phones are embedded with sensors already — and include location-tracking GPS and Wi-Fi tech — exposure notification apps seem like they should be easy to create with existing technologies.

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A theoretical notification app could log your location and the locations of other users, much as Google Timeline logs the location of your Android phone already. If another user tested positive, the app could compare their location history to yours, and notify you if you spent time in the same place. It seems like a fairly easy problem for modern tech to solve.

Except it’s not. For starters, an app that constantly logs your location and sends it to a centralized government database would be a privacy nightmare. Any government entity with access to the database could pull up your location history any time they wanted. The implications for biased policing, illegal searches, and other abuses would be monumental. Constantly recording your fine-grained location and sending it off to the government would also be a massive drain on your phone’s battery, data plan, and processor.

Instead of storing it within the government, governments worldwide have worked together with both Apple and Google to create an innovative solution that allows for exposure notifications while keeping your phone snappy, and minimizing the risk to your privacy. The system is built on a protocol that uses the Bluetooth chip in your phone to communicate anonymously with other phones around you.

If you download an app like CA Notify, your phone will constantly look for the Bluetooth signatures of other app users who are physically nearby to you. When it detects another user, it will log their presence, and record how long you spent in their proximity, and approximately how close you were. All this data is stored on your phone — it doesn’t get sent off to a central location, so the risk that it will be used to monitor your movements is minimal. Your phone will also broadcast your own signature, so other users can record when they’re been around you.

If an app user tests positive for the virus, they can log this status in their CA Notify app. CA Notify will then send an anonymous message out to all other app users, with the infected user’s unique signature. This won’t be linked to their identity, so their privacy will be protected.

Your phone will look at this message, and see if the infected person’s signature appears in your phone’s personal list of the people you’ve spent time around. If it does — and if you spent enough time around the infected person that you could potentially have become infected yourself — you’ll get a notification in your own CA Notify app. You can then choose to act on this however you’d like. CA Notify and the system behind it is an elegant compromise between keeping people informed and respecting their privacy (and the costs to their data plan).

I downloaded the app this morning and will be experimenting with it more to see exactly how it works. The app itself is simple, with just a few tabs — Exposures, Notify Others, and Settings, which allows users to determine if they’d like to share additional performance and analytics information with the state.

The app’s effectiveness will likely depend on how many Californians download it, and how well it filters out false positives. If you get a notification for every Covid-19 positive person you drive past (or everyone you’re within 100 yards of, even if they’re in a different building), people will likely get fed up and abandon the app. But if it automates the process of informing people about exposures, takes some burden off of contact tracers, and empowers citizens to manage and reduce their own exposure risk, the app could be hugely beneficial.

I could see a future where exposure notifications are gamified. Just as people try to maximize their steps with a Fitbit, they could try to minimize their potential exposures by social distancing, going to businesses at less crowded times, and the like. It may be only a matter of time before a screenshot of the app showing “No Exposures” becomes a social media badge of honor, showing others that you’re taking Covid-19 measures seriously.

Around 20 other U.S. states have already launched notification apps of their own, based on the same Apple/Google system. If you’re a Californian, consider checking out CA Notify today. If you’re not, check and see if your own state has a similar app, and see if it proves helpful in your own personal fight against the pandemic.