Mysteries of being Human

1. Why do we sneeze?
2. Where do 'the chills' come from?
3. Since when do little microorganisms think they can invade the well oiled machine that is my body?!?
3a. How do microorganisms make me sneeze?
3b. Where is the internal Lysol?

and one last one: Do microorganisms get 'the chills'?