Complete sequence of echovirus 23 and its relationship to echovirus 22 and other human enteroviruses.

To define the relationship between echovirus 23 (E23) and other human enteroviruses, we have determined the complete nucleotide sequence of a strain of E23 isolated from a child with high fever in Connecticut in 1986 and compared the nucleotide and deduced amino acid sequences with those of other enteroviruses representing each of the major enterovirus phylogenetic groups, poliovirus type 1, coxsackievirus A16, coxsackievirus B3, echovirus 22 (E22), and enterovirus 70. The genome of E23 (strain CT86-6760) was 7352 nucleotides in length, exclusive of the poly(A) tail, and the genome organization was typical of the picornaviruses. The nucleotide sequence and deduced amino acid sequences were most related to those of E22, a virus with which E23 shares many biological properties, and was quite divergent from the sequences of other enteroviruses (< 20% average amino sequence identity). These data lend further support to the suggestion that E22 and E23 are distinct from members of the Enterovirus genus and that they should be reclassified in a separate genus within the Picornaviridae.