[yovagoyu]

This is hearsay, but I recall being at the Precision Medicine Conference recently and one of the speakers said that when sick with, say, flu, your heart rate spikes maybe 30-60 minutes before you'd otherwise know (have a fever, headache, etc.). So it didn't seem like a very useful test.

Maybe coronavirus is different though. I would check up on sources.

[jniedrauer]

I use a garmin watch and I can confirm this. I had a very high fever about a month ago, so I got to see all the metrics in action. My resting heart rate did not spike until I already had symptoms, making it a useless predictor. Heart rate variability did steadily decline for several days before the onset of symptoms, so that could actually be a useful predictor of infection.