Delirium by Lauren Oliver

Lena     can’t wait for her 18^th birthday because then she will have the procedure which makes her safe from amor deliria nervosa, the deadly disease of love. When Lena gets infected, however, her opinion of society drastically changes. In this futuristic United States, all the people in civilized areas are given the cure for the deliria on or shortly after their 18^th birthday.  Patrols are always on the lookout for signs of emotion or affection and uncured people are immediately treated or eliminated.  This is an exciting book and the start of a trilogy!