Reimagining Exposure Notifications Apps for Broader Public Engagement


PathCheck Foundation has been hard at work developing an open framework again for not only exposure notifications that can be used for more than just COVID-19, but also for crowdsourcing syndromic surveillance in general.

Leveraging smartphones for tracking positive cases of COVID-19 and delivering exposure notifications, all without sharing personal identifiable information between smartphone users, was the groundbreaking innovation that was the impetus for forming the PathCheck Foundation in 2020.  Volunteers from around the globe all joined in to develop the code under an open source license that would also become one of the open standards for contact tracing, and later vaccine verification.

Code developed under our Google Apple Exposure Notification (GAEN) protocol would eventually be built into both Apple’s iOS and Google’s Android operating systems as what has become commonly referred to as Exposure Notification Express (ENX), which has since led to many of the early COVID-19 custom exposure notification (EN) smartphone apps being decommissioned and shut down. This is problematic for a couple of reasons: 1) neither Apple nor Google has any intention to stay in the EN business beyond COVID-19, and 2) all functionality and communications with citizens are no longer controlled by the public health agencies who previously published their own custom applications. This means that if public health agencies want to leverage these technologies for say flu season, Norovirus outbreaks, or Monkeypox, they will not be able to do so under the current native frameworks available to them, at least not without having to reinvent the wheel, which none of them will have the funding to do after COVID-19.

So my colleagues and I at the PathCheck Foundation have been hard at work developing an open framework again for not only exposure notifications that can be used for more than just COVID-19, but also for crowdsourcing syndromic surveillance in general.  Our founder Dr. Ramesh Raskar, PhD from MIT Media Lab has spoken numerous times about what the pandemic journey can look like when leveraging modern technologies and likened these capabilities to developing a ‘Waze for our Pandemic Journey.’

In my own experience developing the Sickweather app and the cold and flu forecasts for IBM’s Weather Company, my team created a version of exposure notifications that we called SickZone Alerts. App users could simply turn off/on the different symptoms and illnesses that people were reporting on social media to create geofenced areas that would trigger an alert to the app user when they crossed that boundary with their smartphone. The SickZones themselves only existed for 2 weeks from the time of the initial report; timing that was meant to approximate the average viral life cycle. It was a simple solution to a very complex problem, but proved to be too noisy for most of the app users, and too burdensome on battery life, so the practice of geofencing all data points would be abandoned.

When I joined the PathCheck Foundation, I saw it as an opportunity to re-envision my previous work in novel disease detection through a pandemic lens with the tools that PathCheck’s team had developed. This has led to the creation of our new flagship PathCheck mobile application. While the app is still in development, I want to share with you how we are thinking about exposure notifications with a new Exposure Map screen that allows the users to place what we are calling Exposure Sensors.

Screen Shot 2022-09-30 at 3.19.03 PMScreen Shot 2022-09-30 at 3.20.29 PM

Exposure Sensors are like virtual, disease motion detectors that alert you whenever other PathCheckers (PathCheck app users) who have recently reported symptoms that enter or overlap with your sensor area, or when public health agencies and other data partners report alerts in the locales where the sensors are located. Initially, the user may place up to 2 Exposure Sensors at any given time. If you want more sensors, you will need to earn them with various app activities that incentivize participation.

You can use Exposure Sensors to receive notifications for the locations you care about the most, including where you live, work, go to school, shop, eat, or perhaps where you are planning a vacation and other travel destinations – to help you know before you go!

The concept of Exposure Sensors may seem simple, but it solves a few problems. Instead of mapping and geofencing all data points and locations, it relies on the locations that matter most to the users, and only when those locations are tripped by others, thus reducing the burden of data storage, data analysis and visualization challenges, as well as preventing unnecessary alerts. It also inherently leverages sharding, split learning and other best practices of No Peek Privacy to distribute data on a need-to-know basis while minimizing (and potentially removing) the need for location services.  And by allowing the user to create persistent zones of exposure, they aren’t just getting alerts of the individual people with whom they physically intersect that are opted into Bluetooth-based exposure notifications in Android and iOS. Of which usually results in too few notifications to be helpful – misrepresenting the true risk of communicable disease within the population.

The biggest challenge of course will be having enough PathCheckers to be effective, but we know from COVID-19 that an astounding 40% of all smartphone users turned on Exposure Notifications. So with many of those EN services now being decommissioned and plenty of people who still want to be informed, there is a good chance participation will still be meaningful, even if it’s not 40%. Case in point, a traffic app like Waze needs only 1% of the driving population to use its service in order to be able to represent traffic accurately.

Wazers are incentivized to use the app in order to get timely traffic information, but they must turn on location services for it to work, and in doing so, more traffic data is collected.  Likewise, PathCheckers will be incentivized to participate if they want to get value out of it.  It’s a social contract that if successful will forever change how people monitor and receive exposure notifications beyond COVID-19.  

And that’s just one of the 3 main features being developed for the new PathCheck app. Stay tuned and stay healthy!