(a) Assumptions. We assumed that at the outset of the epidemic the entire population is fully susceptible to infection with the influenza A/H1N1 virus. Infectiousness was assumed to be equal in symptomatic and asymptomatic persons. This is based on the rationale that a lower degree of infectiousness is coupled with unrestricted mobility resulting in a higher number of potentially infectious contacts. In comparison, a higher degree of infectiousness in symptomatic patients is compensated by the reduction of the number of contacts, because patients are isolated and bedbound.