Contribution of trade movements (MV) and neighbourhood contacts (NB) to regional BVDV spread. A Number of infected herds (i.e. having at least one persistently (P) or transiently (T) infected animal) according to the transmission route activated (black: both routes (NB + MV); red: only NB; blue: only MV). B Number of herds getting newly infected (i.e. having one P or T animal at time t while none at time t − 1) when both transmission routes were activated, according to the causal route (red: NB; blue: MV). Green stripes show pasture periods during which neighbourhood contacts occurred, shadows show 25th–75th percentiles illustrating stochastic fluctuations (100 runs), and lines correspond to median values.