Submitted by the MVCAC VVBD Committee
Hills SL, Vu HM, et al. (2026). PLoS Negl Trop Dis 20(8): e0014641. https://doi.org/10.1371/journal.pntd.0014641
Abstract.
Japanese encephalitis (JE), a mosquito‑borne, vaccine‑preventable disease, is endemic to much of Asia and parts of Oceania. Its main clinical manifestation, encephalitis, is associated with a 20–30% case-fatality rate and long-term sequelae in 30%–50% of survivors. During the past two decades, substantial progress has been made in JE prevention and control. Notably, several countries have introduced JE vaccine into their national immunization programs, leading to marked reductions in morbidity and mortality. Nonetheless, major challenges remain, particularly because the disease cannot be eradicated meaning high-quality, long-term JE vaccination programs must be maintained. In addition, JEV has emerged in an increasingly wide geographic area, including in widespread parts of Australia, and shifts in the age distribution of cases towards adults in some JE-endemic areas have occurred. In this review, we summarize current knowledge on JE, outline recent advances in prevention and control, and describe key persisting and emerging concerns. Addressing these issues and continuing efforts to strengthen JE immunization programs will be important to reducing the burden of this disease for populations in endemic areas now and in the future.
Note: Increasing commerce and travel between California and Asia provide some risk for this virus’s introduction. JEV is closely related antigenically to WNV and SLEV, and if introduced into California would most likely be transmitted by the same vectors. Like WNV, equines are susceptible to infection and may develop neuroinvasive disease. This paper relies on historical studies in Japan to incriminate ardeid birds and pigs as the main vertebrate hosts and Culex tritaeniorhynchus as the main vector; however, other Culex and avian hosts have been implicated in India and Pakistan, especially in Muslim areas where swine culture is uncommon.