Figure 1.

Model-predicted persistence and seroprevalence patterns of swine IAV on finishing and farrow-to-finish farms. (a) The probability of stochastic fade-out of infection is plotted for finishing herds ranging in size from 250 to 5000 pigs and farrow-to-finish farms with 300–3000 finishing pigs. The coloured lines represent the model-predicted probability of fade-out for values of R₀ between 1.5 and 5, while the dashed black line represents F = 0.05. (b) The model-predicted mean seroprevalence of influenza prior to slaughter (22–24 weeks of age) is represented by the coloured lines, while the shaded regions between the dotted coloured lines represent the corresponding 95% prediction intervals. The black circles represent the mean seroprevalence of H1N1, H1N2 and H3N2 antibodies observed among finishing pigs from farms of varying size in The Netherlands, while the black lines are the corresponding 95% CIs. Births and the movement of pigs from one site to the next are assumed to occur weekly or every three weeks, as indicated.