Figure 2:

Comparison of R₀ values calculated for multivariate normally-distributed (solid line) and log-normally-distributed (dashed line) heterogeneities for differing values of the correlation coefficient, $r_{X_1,X_3}$, between the biting rate, X₁, and average duration of human infection, X₃. Results are presented for three different levels of the heterogeneity in the average duration of human infection: black lines have Var(X₃) = 4 (these are the lines that appear in Figure (1); blue lines have Var(X₃) = 1, while red lines have Var(X₃) = 10. As in Figure (1), X₁ and X₃ are taken to have means equal to 1 and 5, respectively, and Var(X₁) = 0.2. The value of the susceptibility parameter was fixed at 1 for the entire population. The horizontal dashed line denotes the value of R₀ if there was no heterogeneity, i.e. obtained using the average value, $R_0^{\mathrm{hom}}$.