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Contact Tracing Using Ethica

Learn about Ethica's minute-level contact tracking solution during the COVID-19 pandemic, while preserving individual privacy.
Contact Tracing Using Ethica


One of the features of Ethica is automatically tracking contact of the study participants. This dates back when we were working on Ethica as a research project at the University of Saskatchewan. The first implementation was during the H1N1 pandemic back in the winter of 2009. It used pocket-sized custom hardware to track the proximity of participants. The results were published in a paper titled "Flunet: automated tracking of contacts during flu season".

When we started Ethica in 2016, one of the early projects in collaboration with Harvard School of Public Health also was designed around automatic contact tracing. There, we used Bluetooth from the participant's phone to capture the proximity to other participants with the app. Later in 2018 we also offered the use of Bluetooth Beacons as an alternative method to capture contact tracing. Currently, 56 research projects are using this feature in the Netherlands, Australia, and Canada.

With the recent COVID-19 pandemic, the conversation about contact tracing is everywhere. There are different perspectives on its benefits in a widespread pandemic like COVID-19. There are also different technical approaches to implement such a solution, with the most two commons being the use of Bluetooth and GPS. GPS allows tracking location and inferring proximity from it as done in the MIT PrivateKit. Alternatively, Bluetooth can be used to scan other people in proximity, as done by Singapore TraceTogether or Covid Watch, and as we have done in Ethica since 2010. There are other less-common solutions too such as using microphones by the Austrian Red Cross.

Bluetooth. Why and How?

In Ethica, we have relied on using Bluetooth for contact tracing. The platform supports both the use of Bluetooth hardware in smartphones and Bluetooth beacons. This offers a few important advantages over the use of GPS:

  • GPS data is considerably richer than Bluetooth, which makes it harder to anonymize effectively. This increases the risk of leaking sensitive data in case of a security attack.
  • GPS is not very reliable inside large buildings and densely constructed areas, nor it can be used to detect elevation accurately. For example, it cannot differentiate between different floors of a highrise and considers everyone in the highrise as being in contact.
  • GPS drains more battery both for getting location fix from the satellite and for processing the data. This can negatively impact user experience and lowers the adherence.
  • People rightfully perceive GPS as a more privacy-intrusive method than using Bluetooth. This can make large-scale adoption if the method a challenge.

For all of the above reasons, we have been advocating to use Bluetooth (specifically Bluetooth Low-Energy or BLE) for contact tracing.

In this model, when a user installs the Ethica app, the app continuously announces its presence in the surrounding environment by sending a specific signal. At the same time, the app listens for the signal from other phones. When it receives a signal from another device, it records the presence of that device. It also records the relative distance of visiting device based on the received signal strength indicator, or RSSI. While RSSI to distance conversion has its own limitations, for distances less than 2 meters or 6 ft it's fairly reliable.

The main drawback of this approach is that the accuracy of the recorded contact network depends on the adoption rate by the community. The more people use the app, the more complete is the captured contact network for each person.

Our Solution

We have prepared a customized app for collecting people's contact network during the COVID-19 pandemic. The app uses most of the features from our native Ethica research app for Android and iOS, with a few differences:

  1. By default, it uses Bluetooth Low Energy available in the user's phone to broadcast and listen to other users in proximity and record the user's contact network.
  2. It does not upload the collected data unless a security PIN is provided to the user from a public health staffer. This ensures the only way to access the contact network data involves both a healthcare worker and the user. This decentralized model increases the security of the data as well.
  3. Data older than a certain period (3 weeks by default) is removed from the device.

Similar to the Ethica research app, this customized app allows configuring the home page of the app by adding surveys, informative content, or relevant materials, as necessary. The interface is also available in 8 languages, including French and Spanish.

The customized app can also be branded for specific health regions. This branding helps considerably with the community's trust in the app and can increase the adoption rate and lead to more accurate data collection.

The following video walks you through the entire process:

We are currently discussing the deployment of this solution in a few provincial health authorities across Canada, and we hope to have our first rollout in the upcoming week. If you are interested to know more about this solution, please contact me at mohammad@ethicadata.com.