Fig. 4

The effect of competition cost of clade Y on 2008–2009 seasonal influenza A/H1N1 epidemic simulation. With R _0max and R _0min fixed at 2.00 and 1.61 respectively, while clade Z assuming relative fitness of 1.00 (Strain Z _1.00), the model generated the dynamic behavior of clade Y with competition cost between 0.00 (Strain Y _1.00) and 0.90 (Strain Y _0.10). The Strain Y _0.29 coupled with 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