BACKGROUND: The
prevalence and the origin of
HIV-1 subtype B, the most
prevalent circulating
clade among the long-term residents in Europe, have been studied extensively. However the spatial
diffusion of the
epidemic from the perspective of the
virus has not previously been traced. RESULTS: In the current study we
inferred the migration history of
HIV-1 subtype B by way of a phylogeography of viral sequences sampled from 16 European countries and Israel. Migration events were
inferred from viral
phylogenies by character reconstruction using parsimony. With regard to the spatial dispersal of the
HIV subtype B sequences across viral
phylogenies, in most of the countries in Europe the
epidemic was introduced by multiple sources and subsequently spread within local networks. Poland provides an
exception where most of the
infections were the result of a single point introduction. According to the significant migratory pathways, we show that there are considerable differences across Europe. Specifically, Greece, Portugal, Serbia and Spain, provide sources shedding
HIV-1; Austria, Belgium and Luxembourg, on the other
hand, are migratory targets, while for Denmark, Germany, Italy, Israel, Norway, the Netherlands, Sweden, Switzerland and the UK we
inferred significant bidirectional migration. For Poland no significant migratory pathways were
inferred. CONCLUSION: Subtype B phylogeographies provide a new insight about the geographical distribution of viral lineages, as well as the significant pathways of
virus dispersal across Europe, suggesting that intervention strategies should also address tourists, travellers and migrants.
