Figure 1: Model scheme. The 32 state variables are denoted by n + subscript. All pools other than the virus pool () and the dead-from-influenza pool () suffer from a natural mortality rate of μ (Table 1, where parameters are listed). Many categories (e.g., “Infected”) consist of sequential pools. The four infected pools all have (incubation) rate constants of . Similarly, applies to the four nonhospitalized clinically sick pools, to the three hospitalized clinically sick pools, to the seven asymptomatic pools, and to the ten pools in the loss-of-immunity delay pipe. and are the fractions of the fluxes between and , and and , which are asymptomatic and hospitalized. and are the death rates (caused by flu) of the clinically sick and hospitalized pools.