Molecular epidemiology of echovirus 30: temporal circulation and prevalence of single lineages

Echovirus 30 (EV30) is one of the most frequently isolated EVs, causing extensive outbreaks of EV30 aseptic meningitis in temperate climates. EV30 is antigenically heterogeneous, and three major antigenic groups have been defined, although the basis for the antigenic differences is unknown. A reverse transcription-nested PCR which amplifies the 3'-terminal region of the VP1 gene directly from clinical samples was selected for studying EV30 molecular epidemiology, since the major antigenic sites in this region reflect the serotypic pattern of this virus. The different previous approaches to the genetic classification of EV30 were analyzed. A complete study of the EV30 strains was performed by analyzing the sequences from the 112 EV30 strains amplified in this work and the complete set of EV30 strains previously published. A total of 318 strains of EV30 were divided into two broad genotypes (I and II). This classification was supported by the phylogenetic trees obtained from amino acid sequences, and it correlated with the antigenic heterogeneity of the reference strains described in earlier studies. The genotypes could be further divided into subgroups, and these subgroups could be divided into lineages based on their nucleotide distances and levels of bootstrapping. On the other hand, the subgroups and lineages did not result in the same correlation between amino acid and nucleotide differentiation. The molecular epidemiology of EV30 can be compared to influenza virus epidemiology, where prevailing lineages displace the less established lineages on the basis of immune escape. This pattern of evolution is clearly different from that of other enteroviruses. A single lineage at a time appears to be circulating worldwide. This behavior may be related to the epidemic activity of EV30.