The Nepal Ministry of Health and Population reports 133 Japanese encephalitis (JE) cases in the country since the summer, including 31 deaths.
Both deaths and the number of infections are at their highest levels in recent years, health officials say.
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.
Nepal saw 86 cases in 2024, 105 cases in 2023, and 79 cases in 2022.
“We are aware of the rising death toll from JE and are making every effort to make people aware of the risks,” said Dr Abhiyan Gautam, chief of the Immunization Section at the Family Welfare Division under the Department of Health Services. “Mass vaccination of the unvaccinated population could lessen the death rate and prevent severity, but we don’t have vaccines available.”
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.
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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.
It is found mainly in Asia. About 70,000 cases of JE are estimated to occur in Asia each year, although the actual number of cases is likely much higher due to underreporting in rural areas. JE is fatal in approximately 30 percent of those who show symptoms, and leaves half of survivors with permanent brain damage. The disease is endemic in Southeast Asia, India and China, a region with a population of more than three billion.