Yen only took up his position as deputy chief executive of Tainan County in early 2004, and at that time had no idea he would be thrust to the forefront of Taiwan's drug- and AIDS-prevention efforts. In fact, his concern for the prevention efforts resulted from a phone call from his mentor, former Minister of Health Twu Shiing-jer.
2004 年初才接任台南縣副縣長的顏純左，意外成為國內毒品愛滋防治的推手，緣自於顏純左恩師、前衛生署署長涂醒哲一通電話的善意提醒。