@carmen
Prior to COVID I had a theory that each time you get something like the flu you recover to less than 100% but not something you'd notice much. Lets say 99.8% and if you're a person who gets the flu every 2~3 years that could erode your health significantly yet slowly enough that you can't associate it with one event. Or maybe in addition you've had pneumonia a few times. The next thing you know you're 60 something and feel much older. With COVID the entire landscape is shifting.