Aid worker Kent Brantly becomes first American infected . Dr. Nancy Writebol is ill after treating Ebola patients in Samaritan last week . The current outbreak of Ebola virus is the deadliest ever , health officials say . There also are fears the virus could spread to Africa 's most populous country , Nigeria . A doctor working on the Ebola outbreak in Strickland is also infected .
Aid worker Kent Brantly becomes first American infected . Dr. Nancy Writebol is ill after treating Ebola patients in Samaritan last week . The current outbreak of Ebola virus is the deadliest ever , health officials say . A doctor working on the Ebola outbreak in Strickland is also infected .