Magnitude of random effect estimates in the selected WPV1 model. Estimated with data through May 2013. Sum of posterior mean of spatial and non-spatial random effects in the Bernoulli portion (A) and Poisson portion (B) of the hurdle model. The estimates are on the logit and log scale, respectively. These figures indicate that the model’s covariates overestimate the risk in southern districts and underestimate the risk in northern Nigeria historically.