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Intelligence Analysis

Health Authorities in Nepal Report Highest Number of Japanese Encephalitis Cases since 2015

13 OCT 2025

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2 min read



Culex species mosquito biting skin

Key Takeaways:

  • The number of reported cases of Japanese encephalitis is increasing rapidly in Nepal due to heavy rainfall causing increased mosquito breeding.
  • Although vaccination is not needed for short-term travel to Nepal, if you are engaging in activities in rural areas, it is recommended.
  • Due to a gap in immunization availability in 2006, the most vulnerable population to be infected are unvaccinated agricultural workers over the age of 40 years old.

Nepali health officials have reported 118 confirmed cases of Japanese encephalitis and 23 deaths since Aug. 31; a rapid increase from the 33 cases reported Aug. 12, authorities will likely continue to report additional cases within the coming weeks. The surge reflects escalating mosquito activity due to heavy rainfall during the monsoon season (June-October) and immunization gaps in vulnerable populations. The most affected individuals are unvaccinated agricultural workers above 40 years old (74 percent of cases), and cases are clustered near rice fields or pig and chicken farms.  

Geographic Expansion

Japanese encephalitis has been endemic in Nepal, specifically the Terai Region, since 1978, although geographic expansion of the disease has increased from 18 to 36 districts in the country. Reporting 86 cases in 2024, 105 cases in 2023, and 79 cases in 2022. Historical data show that before a vaccination was introduced, up to 2,000 deaths occurred annually in Terai. As of Sept. 15 the most affected provinces are Lumbini (39 confirmed cases), followed by Bagmati (18 confirmed cases), Koshi (17 confirmed cases), and Gandaki (18 confirmed cases). Recent cases have also been reported in Sudurpaschim (nine cases) and Karnali Province (two cases). 

Symptoms and Transmission

The government has deployed response teams to the most affected areas to provide training to over 2,100 health workers to improve early detection and response capabilities. Awareness and community monitoring campaigns are being implemented to educate the public on symptoms.  

Japanese encephalitis is a preventable viral disease transmitted through the bite of the infected Culex mosquito. Japanese encephalitis virus circulates in pigs, sheep, and water birds. Most infected individuals experience no symptoms or only mild symptoms like fever and headache. The virus does not spread from person to person, and symptoms typically appear 5-15 days after being bitten.  

Vaccination

Vaccination is not necessary for short-term travel to urban areas; however, it is recommended if you will be engaging in activities that increase the risk of infection, such as visiting rural areas, hiking, or camping.  

The Nepal Ministry of Health and Population launched a vaccination campaign in 2006 focusing on the most affected populations in Banke, Bardia, Dang, and Kailali districts, later expanding to other areas. In 2015, the vaccine was integrated into the regular immunization schedule for children under 15. The WHO reports vaccination coverage for Japanese Encephalitis in 2024 to be 94 percent. Individuals who were over 15 years old and therefore not eligible at the time of the campaign are the most affected, accounting for most reported cases. The recent resurgence indicates gaps in ongoing adult immunity. Additional vaccination or catch-up efforts may be necessary to reduce adult mortality rates.   


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