Figure 1.

Effect of demographic stochasticity on influenza epidemics. The classic stochastic SEIR (susceptible, exposed, infectious, recovered) model tailored to the epidemiology of influenza, based on a latent period of 1.5 days, an infectious period of 3 days, basic reproduction number (R₀) of 1.5, and an assumption of homogenous mixing of the population, was used to generate 100 stochastic simulations in two population sizes of n = 1,000 (left panels) and 11,000 individuals (right panels). Simulations were initialized with five infectious individuals. Histograms show a higher probability of epidemic extinction in the lower population setting. Stochastic epidemic realizations are shown in light blue, while the red solid line curve corresponds to the average of the stochastic realizations that resulted in epidemics.