Saints usually become patrons of countries, professions, and special needs through popular devotion rather than by any official designation. They may be closely associated with the history of a country, or have been engaged in some form of work associated with a particular profession, or have performed certain ministries or healings related to special needs.
A saint is a person who is recognized as having an exceptional degree of holiness or likeness or closeness to God. While the English word saint originated in Christianity, historians of religion now use the appellation "in a more general way to refer to the state of special holiness that many religions attribute to certain people" ... Read more at Wikipedia.