Extended Data Fig. 2: Examples of the different groups of sequences identified.

‘Candidate transmission clusters’ are groups of Spanish sequences that form a clade. ‘Zero distance clusters’ are groups of Spanish sequences that are at zero distance from each other. Finally, the ‘unique’ sequences are Spanish sequences that are more than 1 SNP away from any other Spanish sequence and that do not share a most recent common ancestor (MRCA) node with other Spanish sequences.