Whatever it is, do you have one of those small blood oxygen monitors? Both one of my brothers and later my Dad, came this close || to dying of flu induced pnuemonia. My brother permanently lost over 60% of his lung capacity.
I have an Oura ring that monitors your vitals. And I do have a finger sensor. So far just showing a 3 point temp rise before I started taking Doxy.
I am going to monitor very closely because I know how fast something can turn on you when your body capitulates.