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).
Quick Answer. A sister or sister-in-law of a grandmother or grandfather is commonly called a great aunt or, less frequently, a grand aunt.. Amy Johnson Crow of Ancestry.com argues that grand aunt is technically the more correct term, though it is less common. Continue Reading.