My Stepfather had Open Heart Surgery 4 weeks ago (replaced a valve and removed an anerism). His recovery was amazing! Everyone (even doctors) could not believe how well he was doing. Then, exactly 2 weeks later he began with fevers which returned him to the hospital (102 - 103). while in the hospital his temp rose to 108! He remained completely fine otherwise! During the fever episodes he gets uncontrolable chills and shakes. He was released from the hospital after 8 days with no conclusion. His temps stayed around 99. Now, 2 weeks later he is back in the hospital with temps of 103 - 105....MRI s showed nothing, CT Scans show nothing, NUMEROUS blood cultures show nothing! What could be happening? Now, this otherwise completely healthy 64 year old man is getting very worn down, and frustrated to say the least. What could this be?