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Science and Innovations

Arizona Universities Test COVID-19 Smartphone App

Chris Richards/University of Arizona

A new smartphone app can anonymously alert people if they’ve been in close proximity to someone who tested positive for COVID-19.  “COVIDWatch” uses Bluetooth to connect with nearby phones that also have the app installed, and alerts users when they’ve been close to an infected person for a significant amount of time. It’s being tested for the first time at the University of Arizona, and Northern Arizona University is considering adopting it. KNAU’s Melissa Sevigny spoke with Joanna Masel, a professor of ecology and evolutionary biology at the U of A who designed the app’s risk assessment technology.

How does the technology work? How does it figure out if you’re in close proximity to someone?

If you test positive for COVID and you decide to use the app to tell people about that, then you get a secure code that says “yes I really did have COVID, I’m not pranking the system.” When you enter that code in, it will send a key to a server, again, a random set of strings, you can’t tell what it is…. And so every day or six hours, or however long the app is currently working at, it will check that server and say, did I hear any dangerous signals? If it did hear any dangerous signals then it will ask, how dangerous were they? People are most dangerous around the time their symptoms start…. Then it will say, how long did I hear them for, did I hear them over the course of 30 minutes or just once, in a little brief blip? And then how strong was that signal? Was it from a phone fairly close to me or from a phone that was fairly far away? It integrates those three pieces of information, and then decides whether your exposure was significant or not.  

How is this different from traditional contract tracing?

It has a couple of key advantages. It’s faster… and speed is really important. There is very, very little time, between—you could become infectious only a couple of days after you’ve been exposed. It’s important people get told to quarantine as quickly as possible and before their symptoms start…. Another advantage it’s completely anonymous, you don’t talk to a person, nobody needs to knows who you are. It can trace people you don’t know. On a college campus you might sit down and have a 20 minute conversation with somebody, and you don’t know what their name is, you can’t really help a manual contract tracer find them.

Can you tell me about some of the limitations of the app? In other words, what do you have to have in order for it to effectively slow transmission?

Firstly people have to download the app. There’s been a lot of talk about some magic number of how many people have to download it. There is no magic number, what matters is that your contacts and contact’s contacts download the app. If the people around you download it, that will help keep you safe. You have to have testing, and you have to have rapid testing. Contact tracing of any sort is not possible unless test results are coming back quickly. Obviously you have to have a smartphone. The technology demands aren’t too onerous, but they are there, and they don’t include everyone.

Has this type of technology ever been used before?

No, this technology is brand new. It started being discussed to the best of my knowledge for this pandemic. People thought Bluetooth was a great technology to do this with, then they realized it wasn’t working very well on Apple. For that to be fixed Apple and Google were going to have to work together. Some people thought, that’s never going to happen, this technology will never work, and then Apple and Google did come together to work on this and fix things so the technology became possible.

Joanna Masel, thank you so much for speaking with me.

Thank you so much.


Melissa joined KNAU's team in 2015 to report on science, health, and the environment. Her work has appeared nationally on NPR and been featured on Science Friday. She grew up in Tucson, Arizona, where she fell in love with the ecology and geology of the Sonoran desert.
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