Figure 2

Impact of vaccinating aquatic birds (mainly ducks and geese) on the transmissibility of H5N1 influenza in poultry of a province in a South East Asian country. Maximum likelihood estimate (solid line) was made using isolation rates of 1.8% for aquatic birds and 0.26% for chicken [7] (R ₀ = 1.24, α_A = 0.06 and m = 1.86). Dashed lines reflect a simple sensitivity analysis. We refitted the model to the highest and lowest isolation rates not significantly different from 1.8% and 0.26% (with 95% confidence). For simplicity, we assume aquatic birds and chickens mix freely, i.e. at any one time infections are not concentrated in only a few flocks. In this simple illustrative model, we did not account for the interaction between backyard flocks, industrial flocks, free ranging birds and wet markets. Note that these results are sensitive to the relative population sizes of the two groups (not shown). Therefore, further analysis of this system with a more detailed population structure is warranted.