Ten atypical European Borrelia burgdorferi sensu late (Borrelia spp.) strai
ns were genetically characterized, and the diversity was compared to that e
ncountered among related Borrelia spp. from North America. Phylogenetic ana
lyses of a limited region of the genome and of the whole genome extend exis
ting knowledge about borrelial diversity reported earlier in Europe and the
United States. Our results accord with the evidence that North American an
d European strains may have a common ancestry.