Kent Brantly, the Texas doctor who contracted Ebola while working in Liberia, was given an experimental serum before he was flown to the U.S., the Christian aid group Samaritan’s Purse said. Dr. Thomas Frieden, director of the Centers for Disease Control and Prevention, said Sunday that Brantly appears to be improving, less than 24 hours after he was admitted to Emory University Hospital in Atlanta for treatment. Nancy Writebol, the other American infected with ebola, was earlier given the experimental serum. She was expected to arrive in the United States Tuesday to be treated at an Atlanta hospital, sources told NBC News.