The Infectious Disease Impact Scale is a heuristic model based on key principles in disaster sociology that defines a community transitioning from normal routine activities of daily living to crisis and then to disaster conditions. Crisis refers to a need for the community to engage in organized, often multi-agency decision making in response to a perceived hazard or threat. Disaster refers to a hazard or threat that has become manifest in a community and all response mechanisms available to that community have failed. The IDIS is informed by a taxonomy of approximately 100 indicators that define the intersection between the perceived hazard or threat, its impact, and the community's response