In a second example, the combined project focus is to address the problem of "what can be done to mitigate pandemic influenza if it gets established in the U.S." The specific objectives of the combined study are to assess the feasibility and effectiveness of different types of interventions strategies. The types of interventions specifically exclude prepandemic vaccines and limit the available quantity of a partially efficacious vaccine, but utilize as much antiviral treatment as required. Two paradigms are the focus of this study: the entire United States and a large city (Chicago). Six studies (and corresponding models) examine this problem. Two of these models simulate transmission in the continental United States, three others represent transmission in the city of Chicago, and the sixth presents the results of a historical review of the 1918 Spanish influenza epidemic. The last study helped justify the design of the intervention strategies.