The Government of India has developed a mobile tracker app - Aarogya Setu - as part of their efforts to contain the spread of Coronavirus in this country of 1.3 billion people. The app is available for both iPhone and Android phones.

The Aarogya Setu app has already gone viral in India with more than a million downloads in a single day.

The app has three parts:

1. It contains a chat bot that guides you through a self-assessment test if you exhibit any COVID-19 symptoms.
2. The app provides quick access to emergency phone numbers of health centers that are dealing with COVID-19 patients.
3. The app will automatically alert you if you ever come near (or have crossed paths earlier) to a person who has tested COVID-19 positive.

Contact Tracing for COVID-19 - How the app works?

The proximity alert feature in Aarogya Setu is the reason why people are so interested in this app but how does this work?

This morning, a person who returned from Dubai about two weeks ago, tested positive for Coronavirus and the authorities have taken him to the hospital. Their residence is less than a mile from our home and I was expecting some sort of alert in the tracker app but none so far.

So I dug a bit deeper into how the app works and here’s what I found:

When a user installs the app, it uses Bluetooth to detect any nearby phones that could also be running the Aaryogya Setu app. While the actual algorithm is a secret, the app likely keeps a record of all devices that have ever been near to you. If the owner of any of these nearby phones is later found to be infected, the app will alert you.

Thus more and more people have to install the app, with Bluetooth and location turned on, for the proximity alerts to really work.

I am not aware of the internal working of the app but I think it would have been even more effective if it made use of GPS data as well. Let me explain.

When the app is continuously scanning the location of its users, it has a fairly accurate overview of who has been where in recent days. If a COVID-19 positive case is detected, his path can be traced and others users who have crossed through those geographic regions can be alerted though the app.