Saint Louis encephalitis is a disease caused by the mosquito-borne Saint Louis encephalitis virus. Saint Louis encephalitis virus is a member of the family Flaviviridae related to West Nile virus and Japanese encephalitis virus. Saint Louis encephalitis virus is endemic to the New World and is present from southern Canada to Argentina, from the east coast and west coast of the United States, and in the Caribbean Islands. Source: Wikipedia (en)