Molecular epidemiology of echovirus 30 in Europe: succession of dominant sublineages within a single major genotype.

The genetic relationships between 131 echovirus type 30 (E-30) field isolates were studied using phylogenetic analysis of three genomic intervals: VP4/VP2 (420 nt), the entire VP1 and VP1/2A (150 nt). The strains had been isolated between 1975-1998, in different European countries, and in Israel and Japan. The maximum genetic variation was 15.7% in the VP4/VP2 region, 21.3% across the VP1/2A junction and 16.7% in the VP1-gene. The clustering patterns were very similar in all three regions. Two distinct genotypes were observed among the European strains, one of which was prevailing, spanning most of the investigated period. The same genotype was previously described to be the most prevalent circulating lineage of E-30 in Northern America. Interestingly, the two other genotypes comprising the prototype strain Bastianni and the oldest European isolates circulating before 1976, respectively, had apparently disappeared. Furthermore, the oldest lineages of the prevailing genotype had likewise disappeared and the recently isolated strains in the prevailing genotype were genetically quite homogeneous, even when isolated in geographic regions far apart. These results indicate that the genetic variability of echovirus 30 is significantly lower than that of other previously characterized enteroviruses. Furthermore, one single, major genotype showed epidemic spread across two continents. Interestingly, despite the low nucleotide variability, maximum amino acid sequence variability in VP1 was surprisingly high, 8.0%, suggesting possible antigenical differences.