Hi. There is great study from Snyder Labs which reveal heart rate pattern pre- and during covid. Since we know that when HR goes up (marker of disease onset) HRV goes down - HRV may help in same way to predict / diagnose diseases. It’s not specific to COVID, but to many diseases.
Recently i did cluster analysis on my 667 oura ring nights and found clear “sick night” (red) pattern (HRV ruins) and clear “restorative night” (green) pattern when HRV goes up.
It seems HRV is a pretty good biomarker to distinct disease / healthy statuses.