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).
I go to wait on my great-aunt, and a dear, cross old soul she is, too, answered Jo. An aunt of my father's, and consequently a great-aunt of mine, of whom I shall have more to relate by and by, was the principal magnate of our family.