Fig. 4

Analysis of importation events into Denmark and onwards transmission between regions. A The temporal span and development of each transmission cluster, grouped by Danish region. Each transmission cluster is indicated with a solid horizontal line, with points at each week sized according to the number of cases. Circles indicate first observed case of an introduction lineage imported from outside Denmark. Red points indicate presence of cases with travel history in the given week. B The number of introductions into Denmark across time. Colors indicate the total number of offspring cases associated with each introduction lineage. C The relative contribution of introductions versus ongoing existing transmission. Introduction-related cases were defined with various cutoffs for the maximum number of days between the case and the first observed case for each introduction lineage, as indicated by different colors. D The origin of introductions across time for each region. If there was equal support for multiple regions as origin for an introduction Denmark was used as the origin. Label notDK indicates an introduction from outside Denmark. Only ancestral state changes with a marginal probability > 95% were included in the analysis