Our exercises were conducted over a period of several years. While we did not conduct exercises with any health department more than once and did not employ an experimental design to assess changes over time, we were struck by how the performance of health departments overall improved over time. First, compared to earlier exercises, local health departments appeared far more sophisticated about their early internal processes related to notification, enhanced surveillance and large outbreak investigations. In addition, by the end of the exercise period, health departments had considered plans for surge capacity, and participating hospitals had explicit plans for cancelling emergency surgery and discharging less severely ill patients. They also appeared more acutely aware of the challenges in assuring adequate numbers of staff to provide care.