That's rough.I caught an absolutely vicious flu my first year of teaching 20 years ago: lungs so filled with fluid that I couldn't safely lie down, not able to eat for a week, severe body pain (not just "aches"). It took me a month to fully recover. Since then, I have never gotten the flu again. I get colds from my students annually & even got strep once, but never again the flu- I don't even bother with the shot anymore. I think my immune system never forgot that battle.
I haven't gotten sick as much since retiring, but got sick upon returning from France/Belgium in late January of 2020, and then again shortly after returning from DL California in late February.