The reason I ask is because our bodies as human beings have an amazing immune system and unless you have an autoimmune disease, naturally our bodies can heal ourselves from sickness.
I’m speaking primarily on the common cold, Influenza or anything similar like it, including even COVID.
Humanity was regularly decimated by diseases we had no defences for across our entire history. It was a major factor the fall of several major empires. Just because it didn’t annihilate the entire species doesn’t mean we “survived fine”.