Detection of novel Echovirus 25 lineage from patients and sewage in Fukuoka in 2024

Echovirus 25 (E25), belonging to the Enterovirus B species of viruses, is known to cause infectious gastroenteriris, aseptic meningitis, and acute flaccid paralysis. Our study aims to conduct enterovirus surveillance and subsequent molecular epidemiology investigations among patients and sewage samples in Fukuoka. In 2024, a total of ten and seven enteroviral strains were detected in 141 clinical specimens and 24 sewage samples, respectively. Among them, five E25 strains were identified, and phylogenetic analysis of VP1 region revealed that these strains constituted a distinct clade separated from previously reported E25 strains. Full-length genome sequences were determined using sequence-independent, single-primer amplification and next-generation sequencing. The five strains had sequence identities ranging from 99.0% to 99.9% among themselves. Through phylogenetic analysis, the five strains were classified as E25 on the basis of P1, and P1–3 sequences, and as E3 and E11 on the basis of P2–3 sequence. Furthermore, SimPlot and RDP4 analysis revealed a unique recombination event between the detected E25 strains and E3 in the region of the 2B gene, which is the non-structural region. These findings indicated the emergence of a novel E25 lineage in 2024, and underscore the importance of continued surveillance to monitor its evolution and circulation.