Figure 7.

The effect of prior exposure on PAM induced morbidity during epidemic outbreaks. High year-round transmission results in most women experiencing PAM some time during their first pregnancies and offers a high degree of protection within the multigravidae class. Low levels of transmission on the other hand leave women of all parities vulnerable to the disease, causing a high degree of excess morbidity during large epidemics. Parameter values: μ = 1/40, m = 1/14, c = 1, B = 1/40, α = 0.1, H = 10, k = 10, λ_S = 0.5-λ₀.