system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What do viruses/bacteria exactly do inside of our bodies that makes them dangerous and causes us to get sick?
gpt
Just a little additional info:

When you "feel sick" most of these symptoms are not caused directly by the infection, but by your own immune system attempting to kill/flush out the infection.

Fever to kill the infection

Runny nose (increased secretion) to flush out the system 

Cough/sneeze. To expel built up secretions and infectious organisms.


In fact allergies are just your immune system reacting to things that aren't pathogens.