 "propositus" or "proband") that stimulates investigation of other members of the family to discover a possible genetic factor.The term can also be used in non-medical fields to describe the first individual affected by something negative that since propagated to others, such as the first user on a network infected by malware.In the early years of the AIDS epidemic, a "patient zero" transmission scenario was compiled by Dr. William Darrow and colleagues at the United States Centers for Disease Control and Prevention (CDC).