My dad is 70 yrs old and has been running a high fever from 102-104 for 4 days. He has no pain, no cough, no other symptoms really other than being tired and listless. He has had hard rigors during this time also and while he has fever, even when as low as 100.2, his mind is confused. Once fever gets down to normal though, immediately his mind is 100% fine and he is his old self. He is in the hospital, has had tons of blood tests, x-ray and cat scan. They have yet to find anything other than a small spot of pneumonia which seems would have been knocked out by the antibiotics by now. Has to be infection somewhere!