Why do you get a fever when the flu?

The body’s immune system causes a fever when the body contracts an infection or another type of illness, including the flu. An elevated temperature is the human body’s attempt to fight off the invasion. In response to an infection, the brain signals the body to raise the temperature. Increased temperatures assist white blood cells in moving more quickly through the body and enhance their ability to fight invading microorganisms. Moreover, higher temperatures impede pathogens from reproducing.