Phylogenetic analysis of complete VP1 sequences of echoviruses 11 and 6: high genetic diversity and circulation of genotypes with a wide geographical and temporal range.

Echovirus 6 (E6) and echovirus 11 (E11) are common causes of meningitis and other human diseases; they are among the most frequently isolated enteroviruses worldwide. In the present work we have studied genetic variability over the entire VP1 gene of selected isolates representing a wide geographical and temporal range. Fifty new sequences from North Africa were included, together with previously published sequences from different countries. The sequence diversity between strains of the same type was high: 22 and 30 % for E6 and E11, respectively. Phylogenetic analysis revealed five genogroups within each type, the genetic diversity within a genogroup generally being <20 %. Some genogroups were further subdivided into genotypes, most containing isolates that had circulated over a wide geographical (several countries from different continents) and temporal (up to two decades) range. Several genotypes were also shown to co-circulate in a region during the same period of time. These features differ from other enteroviruses that divide into temporal or geographical clusters. This study reports new sequences from North Africa, updates the molecular epidemiology of E6 and E11, and proposes a new genogroup in each type.