Why old peoples and children get affected early by diseases
Immune system is responsible for affecting with the foreign bodies or germs and getting affected by the diseases. In childrens the immune system is lower in size and not powerful so as we grow up and reaches at the adult stage, simultaneously the immune system also grows in a large size and at adult stage the immune system will be at its peak level preventing from all type of diseases. Then as we grew much older the immunity also decreases, when we become old, again it reduces to its initial size as it was in the children stage that is reduced size of immune system. This is the reason that children and old peoples get affected early by the diseases as it has much reduced size immunity. Whereas in adults the immune system is at the peak level and at that stage they will not get affected easily by diseases and they are more energetic at that stage and possesing a capability of doing a much work.