How my Breakthrough Covid-19 Infection Showed Up In My Fitbit Data

My fitness tracker saw my infection before I did

Sam Cook

--

A line graph showing a sharp increase that goes out of a set range.

In late July I came down with symptoms consistent with allergies, or a mild cold. I had no sore throat or loss of taste, and I’d been vaccinated for months, so I didn’t think it was Covid. But since I was planning to see friends from out of town over the weekend, I got tested on Friday morning just to be sure. It was positive.

In the midst of canceling all my plans, notifying anyone I’d seen recently, and making work arrangements for my quarantine, I checked my Fitbit app to see if there was anything unusual in what it had recorded. I wear a Fitbit Charge HR almost 24-hours a day, taking it off only to plug it in when I shower. In addition to being a step-counter, the Charge HR collects general health information using a few different sensors, and records it all in the Fitbit app on my phone. When I checked the app that day, one graph immediately jumped out: my average resting heart rate had been spiking for days.

Below I’m going to go through that heart rate graph, and the other data points of interest from the Fitbit app. But just to reassure you up front: I’m fine. One week after likely exposure, I had no obvious symptoms, and overall the infection was milder and shorter than most colds I’ve had. I’m in good health, everyone I was in contact with who has gotten tested has had a negative result, and nothing in the data below currently concerns me. I’m not endorsing the Fitbit or fitness trackers in general for the purpose of disease detection. This is purely about some interesting patterns I observed when checking my own, personal data.

Heart Rate

A line graph of resting heartrate, showing a sharp increase in the middle.

The increase to my resting heart rate was the most drastic, clear sign in my Fitbit data that something was off. When I bought my Fitbit in December 2020, my resting heart rate would bounce around in the low 60s — a good, healthy number for an active adult. Once I got my Fitbit, I started trying to supplement my regular walking routine so that I could hit a 10,000 steps/day goal on a regular basis, and I saw a…

--

--

Sam Cook

Former writer for Tested.com and Geek.com, currently a technology professional, teacher, and father. I write about whatever is on my mind.