What Causes Chronic Fever?

My ten year old daughter tested positive for microplasma in dec. 2014. One week later she tested positive for influenza. Two weeks after Microplasma again. Each one she would have a fever and soar throat, loss of voice and terrible cough. Since she has had the same symptoms 3 or four times but all tests come out fine. Currently her temperature stays about 100.4 I alternate Tylenol and ibuprofen which brings her temp to 98.6 for about 3 hrs then it starts climbing again. This has been happening on a regular basis every other week. She has never been like this and am very concerned about why this is happening.