Question

A DOCTOR/ nurse health worker is exposed to more sick people than others in the community. find out why they avoids gting sick themslves??

Answer 1

Because of working with sick people, the nurse or doctor unknowningly gets a mild form of that disease so the immune system knows that how to stop this kind of bacteria or virus as the disease is a mild form.
Thus when the next time the same type of virus enters the nurse or doctor's body, their immune system know what to do when this type of thing enters the body
Hope it helps