Figure 5.
(a) Expected number of skips (nc) calculated using parameters obtained from the fitted stochastic model. The red filled circles show the expected number of skips nc from equation (2.1) using parameters and the fraction of the population susceptible after the initial DENV1 invasion (s0) estimated from the fitted stochastic model. Each circle corresponds to one parameter combination, and we included here all parameter combinations for the fitted model with a seasonal transmission amplitude (δ) of 0.7 (contacts per person per day) and a likelihood value within two log-likelihood units of the maximum-likelihood estimate (MLE). See the electronic supplementary material, figure S15 for expected skips from parameter combinations with different values of δ, and the electronic supplementary material, figure S10 for parameter combinations from the profile of the recovery rate, γ. For comparison purposes, the black line shows the expected number of skips for the deterministic skip calculation from figure 2b with the reporting rate ρ fixed at the literature value of 3%. (b) Probability of epidemic in 1990 under forward stochastic simulation of fitted model. The fitted stochastic model was simulated forward in time from 1986 to 1990 with population growth. A pulse of 20 infected individuals was assumed to arrive each day in January 1990. Each parameter combination within 2 log likelihood units of the MLE was simulated 100 times. The re-emergence probability was calculated by determining the number of simulations in which the susceptible population decreased in 1990. The plot shows re-emergence probability as a function of the process noise intensity σP. Each point represents a single parameter combination. The MLE parameter combination is circled in red.