“…The most common state transition model is an S-I-R model (Kermack and McKendrick, 1927, is the classic reference; Anderson and May, 1991, provide coverage of additional applications, while Su et al, 1992, Royston et al, 1999, Bagni et al, 2002, Homer and Hirsch, 2006, and Udo et al, 2006, provide various epidemiological applications in a system dynamics context). Animals or herds in an S-I-R model can be either susceptible to disease (S), infected with FMD (I), or "removed" (R) from the system through either death, recovery from disease, or vaccination.…”