Pandemic scenarios are very complex due to the wide number of variables and critical aspects which have to be considered. In fact these phenomena evolve quickly with strong inertia and influence of stochastic components (i.e. mutation, human decisions, etc.). Therefore, Modeling & Simulation is often the only approach able to reproduce effectively pandemic dynamics in a realistic way. A methodology for developing such types of models, taking into consideration open-issues generated by pandemic threats is proposed in the paper and human factors are consider as critical element to mode. A methodology that supports quick development of models and fast result achievement is elaborated and described; at the same time, particular attention is given to validation and verification of models.