If you own a smartphone, you’ll soon be able to volunteer for a contact tracing system that could inform you if you’ve been near someone who’s tested positive for coronavirus, Apple and Google announced .
Contact tracing is a medical term for keeping track of someone with a communicable illness' recent physical contacts, to alert those people if they might be at higher risk of either becoming infected or infecting others, as well as to provide early care for any symptoms they might develop. For instance, the WHO’s definition of contact tracing cites Ebola as an example, with the idea being that once a patient is confirmed to have Ebola, healthcare workers interview that patient about their recent activities and form a list of people who may have come into contact with them, so that they can prepare or quarantine those who might have contracted the disease in the time the patient was contagious before seeking care.
With the whole globe now in the grips of the worldwide coronavirus pandemic, governments are now looking to technology giants to help scale up this crucial task. In particular, Android’s Google and iOS’ Apple are stepping up to the plate with a new solution. With smartphones almost being as commonplace to carry as wallets, the companies feel that the data their products give off makes them ideal candidates for mass contact tracing.
“In this spirit of collaboration, Google and Apple are announcing a joint effort to enable the use of Bluetooth technology to help governments and health agencies reduce the spread of the virus,” identical posts on both the Google blog and the Apple Newsroom stated today.
The idea of using cell phone data to track the spread of a disease isn’t exactly new. In fact, a cell phone heat map tracking location data from phones that had congregated on a single Florida beach during spring break this year gained mass popularity on Twitter late this March for showing just how far potentially infected spring breakers could have spread the disease.
This shows the location data of phones that were on a Florida beach during Spring Break. It then shows where those phones traveled.First thing you should note is the importance of social distancing. The second is how much data your phone gives off. pic.twitter.com/iokUX3qjeBMarch 26, 2020
However, what Apple and Google are proposing is different from using location data to track large trends. Instead, the two companies want to bake individual, automatic contact tracing into each of their operating systems, effectively allowing anyone with a smartphone to keep track of when they might have encountered a sick person.
For privacy’s sake, rather than location data, the idea is to use an opt-in bluetooth system that “doesn’t collect personally identifiable information” to let phones track which other phones they’ve come across during the day, and then use that information to help users and public health authorities limit coronavirus spread. Think of it like Nintendo’s 3DS Streetpass functionality, but for public health.
To explain how it works, Google has drawn up a diagram of an example interaction between two fictional users- Bob and Alice. At the start of the interaction, Bob has a 10 minute conversation with Alice on a park bench. Here, their phones exchange what Apple calls “rolling proximity identifiers,” which update every 15 minutes to prevent wireless tracking of the device and are derived from a “daily tracing key” that changes once every 24 hours. A few days later, Bob tests positive for coronavirus and enters the test result into an app from a public health authority. He gives his phone permission to upload his last 14 days of keys to the cloud, at which point Alice’s phone recognizes that she’s come into contact with one of those keys and sends her a notification that she’s been exposed to a person who has tested positive for coronavirus.
At no point in the interaction do Bob and Alice’s keys identify the two to each other or anyone else, and Google promises that the “list of people you’ve been in contact with never leaves your phone.” Additionally, both passive tracking and the upload of keys from a person who has tested positive are opt-in only.
However, the system will be limited to apps at first, which could limit adoption. It’s set to begin rollout in May, when both Apple and Google will release APIs that allow Android and iOS to communicate with each other using “apps from public health authorities,” which will be available on both platforms and will function across operating systems, meaning that a Pixel user and an iPhone user will still be able to track if they’ve come into contact with each other.
In the future, the two companies say that they are planning to build this functionality into Android and iOS themselves, to allow more people to participate and to allow a phone’s whole app ecosystem to use its contact tracing data.
Each company promises that “user privacy and security” are “central to the design,” with the hope being that anonymous keys, opt-in procedures, limiting who has access to collected data and using bluetooth instead of location data will encourage smartphone users to participate. Additionally, each company’s central servers will only maintain a database of shared keys, with local phones being where matches are tracked. Earlier this week, the American Civil Liberties Union warned against using phone data to track users during an epidemic, but largely focused on location data, which this solution seeks to avoid.
Unfortunately, this privacy-motivated switch to bluetooth does come with its own unique limitations. If keys only last for 15 minutes at a time, phones might have difficulty differentiating between individuals who spend extended periods of time together and those who simply pass each other on the street. Additionally, Bluetooth can’t detect walls, which might cause individuals in adjacent rooms who were never exposed to each other to worry unnecessarily if one of them tests positive. There’s also the larger question of how failure to update either contact tracing apps or eventually operating systems could impact the system, especially in areas with low connectivity. Further, tests are limited right now, which could limit the app's usefulness to certain communities.
Still, as a supplement to more traditional contact tracing interviews, the information offered here is, at the very least, more useful than knowing if you’ve met Lonk from Pennsylvania.