Table 2.

Elasticity indices of (a) the basic reproduction number R₀ and (b) the backward bifurcation threshold value $R_0^{bb}$, computed at the parameter values in Table 1 with γ̃_h = 1/30 and ρ_h = 9 ×10⁻³. These indices quantify relative changes in R₀ and $R_0^{bb}$ in response to corresponding changes in the parameters. The magnitude of an index provides an indication of how sensitive R₀ (respectively, $R_0^{bb}$) is to a parameter, while the sign indicates the direction of change; i.e., whether R₀ or $R_0^{bb}$ increases as the parameter increases (+) or R₀ (respectively, $R_0^{bb}$) decreases as the parameter increases (−). The elasticity indices are presented in order of decreasing magnitude.

Parameter	Elasticity index	Parameter	Elasticity index
(a) Elasticity indices of the basic reproduction number R0.
b	−1.5408	γ̃h	−0.4279
βmax	+0.9888	α	−0.3905
μv0	−0.8242	νv	+0.2611
Λh	−0.5000	σ̃h	−0.0562
Λv	+0.5000	θ	+0.0114
phv	+0.5000	ρh	−0.0113
pvh	+0.5000	βmin	+0.0112
μh	+0.4980	δh	−0.0009
μv1	−0.4368	νh	+0.0003
(b) Elasticity indices of the threshold value of the basic reproduction number, $R_0^{bb}$.
b	+7.6150	phv	−0.8608
βmax	−1.8939	α	+0.8478
μv0	+1.2403	νv	−0.6158
Λh	+1.1002	σ̃h	+0.2471
pvh	−1.1002	μh	−0.1892
Λv	−1.1002	νh	−0.1025
γ̃h	+1.0125	ρh	−0.0867
μv1	+0.9674	βmin	−0.0671
δh	−0.8812	θ	−0.0196