Headache. Many different types of viral infections can cause a fever. In mumps, it is usually a side effect of your body’s defense system kicking in, sometimes before you even know something is wrong. A fever, the production of a chemical that is produced by proteins in your cells as a defensive response to viruses, or other immune system reactions can lead up to you having a bad headache. If you are infected by mumps, your likelihood of getting a headache is about 50 percent. You can relieve some of the pain with the use of an over-the-counter pain reliever. Staying hydrated is also important and getting some rest can make symptoms tolerable while giving your body some time to combat your illness.