Apple and Google are not building contact tracing apps.
"Starting today, our Exposure Notifications technology is available to public health agencies on both iOS and Android," Apple and Google said in a statement.
"Today, this technology is in the hands of public health agencies across the world who will take the lead and we will continue to support their efforts."
After an individual downloads and enables a contact tracing application on his phone, he would subsequently receive an alert if he is exposed to anyone who is diagnosed with or likely to have COVID-19. Of course, that assumes that the COVID-19-positive individual also has the application enabled on his phone.
The companies said that digital contact tracing is meant to augment traditional human-to-human tracing, not replace it. Digital contact tracing is faster than traditional tracing, requires fewer resources and since it doesn't rely on human memory, can make it easier to track exposure in crowded spaces, or contact with strangers.
On the other hand, for such applications to be effective, they require users to download and enable the applications on their phones, and it's not yet clear that Americans will be willing to do so en masse.
One model, by the University of Oxford, found that for digital contact tracing to be effective, 60% of the population would have to opt in. Lower adoption rates could still have a positive effect, the researchers noted.
To reach such a high level of participation, Americans will need to trust that their private health data will be protected, something technology companies that collect health data, including 23andMe, AncestryDNA and MyHeritage, have struggled with in recent years.
There's also a question of how applications will verify positive COVID-19 tests, and guard against people flooding the system with false diagnoses. (Google and Apple say verifying diagnoses will be left up to individual health authorities to decide how to address.) From a practical standpoint, the apps, which require Bluetooth, have to avoid draining users' battery life if public health departments are expecting Americans to use them.
Apple and Google got input from public health associations, including the Centers for Disease Control and Prevention, nonprofits, government officials, academics and privacy experts in order to address some of those concerns, the companies said.
Working together to design the system means that Android and iPhone applications, as well as applications from different states, will be able to recognize one another.
Once they download the app, users will have to consent to make their information available to the health authorities and can turn it on and off when they choose to. Data collection will be kept private and only used by health authorities for COVID-19 exposure, not stored in a central database.
Both Apple and Google said that they will not monetize the data that comes out of the exposure notification system.