Detection of Japanese encephalitis virus in Culex tritaeniorhynchus following the 2024 Noto Peninsula earthquake, Japan.

Japanese encephalitis virus (JEV) is a mosquito-borne zoonotic flavivirus transmitted primarily by Culex (Cx.) tritaeniorhynchus and the risk of JEV transmission is influenced by environmental and ecological conditions. Large-scale natural disasters can substantially alter local environments and mosquito habitats, potentially affecting the circulation of arboviruses. Following the January 1, 2024, Noto earthquake, the surrounding environment in the region changed drastically. In this study, we investigated the prevalence and genetic characteristics of JEV in mosquito populations collected before and after an earthquake in the affected areas and its surrounding region. The climatic and environmental conditions during the sampling periods were also compared to assess their potential contribution to changes in JEV positivity. Despite the lack of statistical significance, JEV was detected exclusively in post-earthquake mosquito samples, and all the detected strains belonged to genotype Ib (GI-b). A phylogenetic analysis further revealed the presence of distinct clades within GI-b, suggesting that multiple independent introduction events had occurred in the past. The detection of multiple sequences of JEV GI-b in mosquitoes collected after an earthquake warrants particular attention, as ongoing post-disaster reconstruction and associated environmental changes may further influence viral circulation, underscoring the need for continued and careful surveillance.