How many feedback loops, and of what type, control the behavior of an epidemic? This seemingly simple question arose on trying to relate the behavior of the epidemic model widely used in K-12 system dynamics to its three-loop feedback structure. A search of the literature discovered two-, three-, and four-loop versions of the basic epidemic model in introductory system dynamics materials. How can the same behavior be explained with such different feedback structures? Can they all be right? This paper will analyze the three basic model structures and discuss implications for system dynamics pedagogy.