Figure 1. Phylogenetic tree showing representative genotype D6 strains identified in Europe before 2005, strains exported from Europe to other continents (source of exportation is shown in brackets), and the D6 variants that were dominant in Europe during 2005 (D6–2000) and 2006 (D6–2005). The phylogenetic tree was calculated on the basis of the 450 nt that code for the C-terminus of the MV N protein, by using MEGA 3.1 software and the neighbor-joining method (500 bootstraps). Genetic distances are represented as numbers of nucleotide differences between strains. Measles virus strains were named according to World Health Organization nomenclature: MVi/City of isolation.Country/epidemiologic week.year of isolation(/isolate number). Sequences obtained from RNA extracted from isolates (MVi) or clinical material (MVs) were distinguished. GenBank accession numbers are also shown for each strain.