Spatial spread and demographic expansion of Lyme borreliosis spirochaetes in Eurasia.

The Lyme borreliosis (LB) group of spirochaetes currently comprises 18 named species that vary in their geographic distribution, host specificity and ability to cause disease in humans. In Europe three species are most abundant, Borrelia afzelii, Borrelia garinii and Borrelia valaisiana but only two of these (B. garinii and B.