Figure 14. The number of human cases with time under the situation that other host species can transmit virus to the original host species.

(a) Migrant birds are viewed as the original transmission source. (a) Resident birds are viewed as the original transmission source. (a) Domestic poultry are viewed as the original transmission source. The intraspecific transmission rates and the interspecific transmission rates are denoted by β_b and β_c, respectively. The changed parameter values can be seen in Table 7.