An American doctor who was infected with Ebola while working with a medical missionary organization in Africa said in a statement that he is feeling "cautiously optimistic" as he fights the deadly virus.  Dr. Peter Stafford was working with the missionary group Serge in the Democratic Republic of Congo when he was infected with the virus, the group said. He was evacuated to a hospital in Berlin, Germany, to receive care, the group said Tuesday. "Before I was evacuated I was feeling really