There's another tool in the toolbox available to fight the spread of COVID-19. Just don't rely on ??? ??????it completely to stay safe.

California Governor Gavin Newsom announced Monday that California's COVID contact-tracing and notification app, CA Notify, would be available and begin functioning on Dec. 10 for everyone in the state with an iPhone or Android device. People who opt in to the system will be able to receive a smartphone notification if they have been exposed to someone who has tested positive for coronavirus (if that person has *also* opted in).

CA Notify is the result of a collaboration between multiple state agencies, the University of California system, other health partners, and Apple and Google. It runs on the Exposure Notification System, which is a technical framework jointly built by Apple and Google, that allows government and health authorities to tap into the anonymized Bluetooth signals of Apple and Android users who opt in, and then send them messages if necessary.

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The system has been available in a pilot program on UC campuses since the fall. But all Californians are now able to opt in. Android users need to download the CA Notify app in the Google Play store. After making sure they have the latest version of iOS, iPhone need to go into Settings, scroll down to "Exposure Notifications," turn that option on, and then select United States > California.

Here's how the system works: If a person tests positive for COVID, they'll get instructions and a code for how to submit that information to CA Notify. The information won't contain personal information like their specific name or phone number. But it will enable the framework to identify the devices of other people that have come in contact with the infected person based on their Bluetooth signals. Exposed people will get a notification that they're potentially at risk and they should get tested, but won't reveal the name or location of their possible exposure. Here's a more detailed breakdown of how it works.

What constitutes exposure? States using the system have the ability to set their own parameters. In California, exposure is within six feet for fifteen minutes or more of someone who has tested positive for coronavirus.

California is not the first state to launch a COVID contact tracing app, but it is the largest to do so. It comes at a crucial moment when cases are surging and putting hospital capacity at risk.

However, if you're relying on a technical system to keep you safe from COVID, the rollout of these apps in other states, and the misgivings of both health and privacy experts, should give you pause.

North Dakota's attempt at digital contact tracing resulted in the collection of imprecise data that only confused contact tracers and made their jobs harder. That's partially because the app can't take into account factors like whether people are separated by a wall, or whether they're wearing personal protective equipment.

Nevada's version of a notification system registered zero exposures in September, a month when COVID was flaring in the state. That speaks to an essential shortcoming of the app: It is more useful the more people actually opt-in.

But making the system opt-in is important from a privacy standpoint. Otherwise we might all get the feeling that the government is tracking our every move. That doesn't mean there isn't cause for privacy concern. The system requires people to keep their Bluetooth on at all times, which makes their devices inherently more vulnerable to hackers trying to steal information about you. Giving the government this access to our smartphones also isn't such a hunky dory idea for the privacy concerned: "It is all too easy for governments to redeploy the infrastructure of surveillance from pandemic containment to political spying," observes the EFF.

However, more tools joining the fight against COVID during this overwhelming surge could ultimately be a positive. Google notes that technical contact tracing is not a replacement for the human run work. But contact tracers don't have the resources to battle singlehandedly against the virus given the immense scale of the spread. In the absence of that work, a notification from an app about possible exposure could prompt someone to get tested and quarantine themself earlier than they might have otherwise, which could slow the spread.

The anonymous aspect of the technical system is also helpful, given the shame some people report upon receiving a positive coronavirus test, which could keep them from sharing the news with others. Like anonymous STD notification systems before it, COVID ones allow people to notify others without revealing themselves.

Notification apps like California's are not the panacea the world needs to end COVID. But, hopefully, it's one more little thing that can help.