Location of study area (simplified coloured polygon) within the target area of southern Ontario. The study area is filled with discrete estimates of herds densities in the study population obtained through kernel smoothing based on Gaussian kernel with fixed bandwidth of 20 km. Estimates are reclassified into 10 categories, and areas with higher intensity of red color represent areas with higher densities of study herds. This density reflects the distribution of swine herds in Ontario. Confidentiality precluded mapping the actual location of herds in the study population.