Comparison of the complete nucleotide sequences of echovirus 7 strain UMMCand the prototype (Wallace) strain demonstrates significant genetic drift over time

The complete nucleotide sequences are reported of two strains of echovirus 7, the prototype Wallace strain (Eo7-Wallace) and a recent Malaysian strain isolated from the cerebrospinal fluid of a child with fatal encephalomyeli tis (Eo7-UMMC strain). The molecular findings corroborate the serological p lacement of the UMMC strain as echovirus 7. Both Eo7-Wallace and Eo7-UMMC b elong to the species human enterovirus B and are most closely related to ec hovirus 11. Eo7-UMMC has undergone significant genetic drift from the proto type strain in the 47 years that separate the isolation of the two viruses. Phylogenetic analysis revealed that Eo7-UMMC did not arise from recombinat ion with another enterovirus serotype. The molecular basis for the severely neurovirulent phenotype of Eo7-UMMC remains unknown. However, it is shown that mutations in the nucleotide sequence of the 5' untranslated region (UT R) of Eo7-UMMC result in changes to the putative structure of the 5' UTR. I t is possible that these changes contribute to the neurovirulence of Eo7-UM MC.