Fig. 3

The effect of relative fitness of clade Z on 2008–2009 seasonal influenza A/H1N1 epidemic simulation. As clade Y assumed competition cost of 0.71 (Strain Y _0.29), with R _0max and R _0min fixed at 2.00 and 1.61 respectively, the model generated epidemic curves of clade Z of a series of relative fitness from 0.80 (Strain Z _0.80) through 1.20 (Strain Z _1.20). Among them, the Strain Z _1.00 simulated the observed weekly A/H1N1 IVIR curve (A/H1N1, shown in black) best and was 96.96% positively correlated. Against the time horizon, the proportion of the total population being infective was plotted on the left vertical axis and the weekly A/H1N1 IVIR on the right