Overview of sample locations in the Norway-wide sampling of Willow Ptarmigan (Lagopus lagopus lagopus), and seroprevalence of louping-ill virus in the different locations. Note that sample sizes are relatively small within locations (range, 1–13). Seroprevalence is here defined as proportion of positive samples out of the total number of samples (i.e., treating equivocal samples as negative). The size of the dot represents the sample size for the location. Local sampling in Njardarheim in 2017 is not shown in this map.