Hello, my 19 year old son has had a fever of 101 to 102 degrees for five days now. Along with the fever, he has chills, body aches, decreased appetite and a headache. I believe this is a virus that his body will fight, but am a bit concerned due to the number of days he has had this fever. What would cause a fever to last for so many days, and should I be concerned that it has lasted so long?