4 year-old's disappearing blood?

My 4 year-old cousin got sick New Year's Day with a virus. He was rushed to the hospital via helicopter. His blood got thin and wouldn't clot. Then his blood started to disappear. They've been having to give him a lot of transfusions to keep the stuff in his body. The doctors have no idea where it's going. Can someone please come up with some disease or something so they can treat it? I don't want the little guy to die, but the doctor's said that he's septic, whatever that is, and that only 10% survive.