Evaluation of model fit. Comparison between the observed verotoxigenic Escherichia coli O157:H7 herd status in a longitudinal observational study from October 2009 to December 2012 (38 months) in 126 cattle herds  (blue filled triangle) and simulated data that replicated that study in 1000 trajectories (boxplot). The figure shows the number of incident cases by quarter i.e. new herds that were found positive in each quarter, and the number of positive herds in each quarter, in total. Q1: January–March, Q2: April–June, Q3: July–September, and Q4: October–December.