In recent years, members of the scientific community have become increasingly alarmed by the threat of a global pandemic caused by a strain of H1N1 influenza popularly known as “bird flu” or “swine flu.” The cause of concern revolves around the especially virulent attributes of the strain of influenza responsible for an estimated 30 to 50 million deaths between 1918 and 1919. The emergence of that strain is thought to have resulted from recombination of portions of the influenza genome of human and avian strains, creating a virus that could be transmitted from human to human, yet so different from previous strains that prior infection conferred no immune protection (CDC 2007). The principle, well established in study of the epidemiology of infectious disease, is that some agents possess attributes that elevate the risk of an epidemic.

Interestingly, although studies of policy diffusion and epidemiology ostensibly explore similar diffusion dynamics, research in interstate policy diffusion has largely overlooked how differences in the properties of policy innovations shape patterns of adoption. Diffusion researchers have focused on understanding how state internal dynamics and interstate interactions produce diffusion patterns, but the influence of the characteristics of policy innovations themselves receives little attention in diffusion research (Karch 2007b). This is surprising because the study of policy diffusion is in essence the study of how new policy ideas interact with states to produce patterns of policy change in federalism.