Fig. 3

Spatiotemporal spread of focal clusters. a Main clusters of focal transmission in Anzio (A1 and A2); colors indicate the date of symptom onset; circles are centered on the index case and have the same radius as the maximal distance of cases from the index case (cluster radius) at the end of the corresponding month. b The main cluster of focal transmission in Rome (R1). c Expansion of the radius over time for clusters A1, A2, and R1. Points are shown at each new record for the cluster radius. Dashed lines represent linear regressions across these points, and their slope indicates the rate of cluster expansion