Figure 2. Natural history of influenza in our model. Duration of each state for a given person is chosen from an exponential distribution. State relative infectivity (IR) and mean state duration were chosen to reflect the infectivity variation of Ferguson et al. (10,11) (see Figure 3). Transition probabilities between presymptomatic and postsymptomatic states are also noted. For symptomatic persons who stay at home, link frequencies outside the household are reduced by 90%.
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