Risk Analysis, Vol. 28, No. 5, 2008 DOI: 10.1111/j.1539-6924.2008.01080.x Risk Communication Planning for the Aftermath of a Plague Bioattack Elizabeth A. Casman 1∗ and Baruch Fischhoff 1,2 We create an inﬂuence diagram of how a plague bioattack could unfold and then use it to identify factors shaping infection risks in many possible scenarios. The inﬂuence diagram and associated explanations provide a compact reference that allows risk communicators to identify key messages for pre-event preparation and testing. It can also be used to answer speciﬁc questions in whatever unique situations arise, considering both the conditions of the attack and the properties of the attacked populations. The inﬂuence diagram allows a quick, visual check of the factors that must be covered when evaluating audience information needs. The documentation provides content for explaining the resultant advice. We show how these tools can help in preparing for crises and responding to them. KEY WORDS: Bioterrorism; inﬂuence diagram; plague ecology; risk communication; rodents; Yersinia pestis 1. INTRODUCTION In a public health emergency, there is little time to develop health communications. Unless that work has been done in advance, public health ofﬁcials must improvise—at the risk of saying wrong things (be- cause the situation has not been analyzed properly) or of saying right things wrongly (because messages have not been tested for effectiveness). If ofﬁcials fail the public, then they can cede the stage to less quali- ﬁed voices, offering conﬁdent, incompetent, and con- tradictory messages. There are guidelines for systematically develop- ing and evaluating communications for well-speciﬁed risks. (1,2) But what happens when a threat’s de- tails cannot be predicted in advance? We propose 1 Department of Engineering and Public Policy, Carnegie Mellon University. 2 Department of Social and Decision Sciences, Carnegie Mellon University. ∗ Address correspondence to Elizabeth A. Casman, Carnegie Mel- lon University, Department of Engineering and Public Policy, Pittsburgh, PA 15213 USA; casman@andrew.cmu.edu. a method for developing communications for such situations. It uses an inﬂuence diagram to organize the facts relevant to the decisions that individuals might face. In advance of an emergency, prototype messages wouldbe developed and evaluated for sce- narios spanning the range of possible emergencies. When an actual emergency arose, the prototype mes- sages would be adapted to the speciﬁc circumstances, drawing on the information organized with the inﬂu- ence diagram. We demonstrate the approach with a plague bioattack, one threat with multiple possible scenarios. 1.1. Current Risk Communication Planning for Plague Attack In focus groups convened by the Centers for Dis- ease Control and Prevention (CDC), participants re- ported wanting information that would help them to prevent and detect exposures, identify symptoms, and treat infections, along with background informa- tion providing them with basic understanding of the hazard. (3) Such information is available on the CDC bioterrorism website. (4) 1327 0272-4332/08/0100-1327$22.00/1 C  2008 Society for Risk Analysis