Japanese Encephalitis Epidemiology and Vaccine Development

Japanese encephalitis virus (JEV) is a mosquito-borne flavivirus that poses a significant public health threat across large parts of Asia and the Western Pacific. Sustained transmission involves a zoonotic cycle in which Culex mosquitoes acquire virus from amplifying hosts, principally waterbirds and domestic pigs, before infecting humans as incidental dead-end hosts. The disease burden remains substantial, with tens of thousands of clinical cases and a high case-fatality rate among those who develop encephalitis. Epidemiological patterns are shaped by rice cultivation, pig rearing, vector ecology and climate, leading to seasonal peaks in temperate zones and year-round transmission in tropical areas. Five genotypes of JEV circulate, and shifts in dominant strains have implications for vaccine performance. Vaccination is the cornerstone of control, with live attenuated, inactivated and chimeric live vaccines deployed in various national immunisation programmes. Recent challenges include the emergence of novel genotypes, limitations in cold-chain and production capacity, and variable cross-protective efficacy of existing vaccines. Next-generation approaches under investigation encompass chimeric platforms, virus-like particles and nanoparticle carriers designed to enhance immunogenicity, simplify manufacturing and broaden genotype coverage. Integrated strategies that combine improved surveillance, targeted vaccination, vector control and risk modelling are critical to reducing the global impact of Japanese encephalitis.

Research from Nature Portfolio

Recent studies have demonstrated that JEV can transmit between pigs via direct oronasal exposure without mosquito vectors, leading to prolonged viral persistence in tonsillar tissue despite high neutralising antibody levels. Experimental infections revealed that pigs shed infectious virus in respiratory secretions and develop similar clinical and histopathological features regardless of inoculation route. These findings challenge the traditional view of strictly mosquito-mediated transmission, suggesting that vector-free pig-to-pig spread may sustain virus circulation in areas with short mosquito seasons. The discovery of non-vector transmission has important implications for surveillance and control strategies, highlighting the need to consider alternative routes of virus maintenance in swine populations.

Japanese Encephalitis Epidemiology and Vaccine Development publication trend

The graph below shows the total number of articles in japanese encephalitis epidemiology and vaccine development across all publications each year (not limited to Nature Index journals).

Technical terms

Seroprevalence: The proportion of a population with detectable antibodies against a specific pathogen, indicating past exposure or infection.

Chimeric vaccine: A vaccine in which genetic elements from a target pathogen are inserted into a well-characterised viral vector to elicit an immune response.

Virus-like particle (VLP): A self-assembling structure composed of viral proteins that mimics the native virus architecture without containing infectious genetic material.

Nanoparticle-based vaccine: A vaccine formulation in which antigens are delivered via nanoscale carriers designed to enhance immune recognition and stability.

Genotype: A classification of viral strains based on genetic sequence variation, often associated with differences in antigenicity and geographic distribution.

References

1. Estimated global incidence of Japanese encephalitis:. Bulletin of the World Health Organization (2011).
2. Review of Climate, Landscape, and Viral Genetics as Drivers of the Japanese Encephalitis Virus Ecology. PLOS Neglected Tropical Diseases (2013).
3. Phylogeography of Japanese Encephalitis Virus: Genotype Is Associated with Climate. PLOS Neglected Tropical Diseases (2013).
4. Low Protective Efficacy of the Current Japanese Encephalitis Vaccine against the Emerging Genotype 5 Japanese Encephalitis Virus. PLOS Neglected Tropical Diseases (2016).
5. Japanese Encephalitis Surveillance and Immunization — Asia and Western Pacific Regions, 2016. MMWR Morbidity and Mortality Weekly Report (2017).
6. Vector-free transmission and persistence of Japanese encephalitis virus in pigs. Nature Communications (2016).
7. Informing an investment case for Japanese encephalitis vaccine introduction in Bangladesh. Science Advances (2024).
8. A chimeric vaccine derived from Australian genotype IV Japanese encephalitis virus protects mice from lethal challenge. npj Vaccines (2024).
9. Advancements in nanoparticle-based vaccine development against Japanese encephalitis virus: a systematic review. Frontiers in Immunology (2024).