High and low risk clusters. Clusters with more (red lines) or less (blue lines) test positive herds than expected based on analysis of results from a bulk milk survey used to investigate the prevalence of antibodies against Coxiella burnetii in Swedish dairy cattle (2008/2009). Cluster analysis was based on exact coordinates and performed using the spatial scan statistic. The numbers within clusters are the calculated relative risk of each cluster compared to areas outside the cluster. ©Lantmäteriet 2013.