Choices, beliefs, and infectious disease dynamics.

A dynamic model of risky behavior in the midst of an epidemic is discussed. The key result is that pessimistic expectations over the future of the epidemic induce more current risky behavior. Numerical simulation of equilibrium epidemics shows that this effect can accelerate spread of the disease in an epidemic's early stages and that the effect of policy interventions, such as preventative vaccines, may depend on whether the intervention was anticipated.