Fever can support the immune system's attempt to gain advantage over infectious agents, such as viruses and bacteria, and it makes the body less favorable as a host for replicating viruses and bacteria, which are temperature sensitive. Infectious agents are not the only causes of fever, however.
Your sister's grandson is your great nephew. You are his great aunt (if you are a woman) or his great uncle (if you are a man).
What relation is my great-niece to my nephew? Paternal is used to refer to anything pertaining to one's father. Maternal refers to the mother, so while a person's paternal grandparents are on the father's side, the maternal grandparents are those found on the mother's side of the family. People also use the terms paternal and maternal to refer to other members of a family tree, such as a maternal aunt or paternal cousins.