My Nephew is Sick

My 6 yr old nephew is being admitted in the hospital. We don't know what is wrong. He is running 103 fever, lethargic, will not eat or drink, his right eye is swollen for no reason. The dr is ordering a ct scan of his brain, they think he may have swelling. They live in FL, so I am dying to be with my brother and sister(in law), and their babies. What could it be? The dr said it looks like something rare!