Fig. 1

Directed acyclic graph of the relationship between model parameters and observed data; for clarity, only one age-group of the stratified model is shown. Distributional and functional relationships are indicated by solid and dashed lines, respectively. Circles indicate model parameters; double circles indicate parameters for which priors (either informative or vague) are applied. N _t and O _t refer to unobserved and observed numbers of individuals at time t, respectively; c _t are conditional probabilities, SIAR _t is the symptomatic infection attack rate, and d refers to detection probability