When you have a need and urge to top more than usual or all the time during sex or sexual activities.
Girlfriend: Want me to top?
Boyfriend:No, I have top fever I need to top.
Top fever is when you feel the urge to want to constantly top the other person during sex or sexual activities.
Girl: Do you want me to top you this time?
Boy: No, I have top fever and need to top you again