What Causes Prolonged Recurring Fever In A Child?

My 7 year-old daughter continues to get a virus that lasts at least 2-3 days each month, in addition to a high to moderate fever. The highest has been 104.5 which required an ER visit, and the lowest temp with 100.5. Blood tests were done 2 months ago, and they came back normal, but she continue to get sick....and miss school.