Over 70 percent of the population over 35 years of age in Nawalparasi East have been inoculated against Japanese encephalitis during the ongoing vaccination campaign. The virus has killed at least six and infected over a dozen in the district since mid-July 2025.

The vaccination was part of preventive measures taken to contain deaths and disabilities from infection, officials say.

“Vaccination started some 10 days ago and will continue until Tuesday,” said Dr Abhiyan Gautam, chief of the Immunisation Section at the Family Welfare Division under the Department of Health Services.”We hope to control the JE outbreak in Nawalparasi East in coming years, as we have vaccinated the previously unvaccinated population.”

JE is a viral brain infection, endemic to Asia and parts of the Western Pacific. According to the World Health Organisation, it is a mosquito-borne flavivirus belonging to the same family as dengue, Zika, yellow fever, and West Nile viruses. The virus kills a third of those who fall ill and leaves up to half of those who survive with severe life-long disabilities, according to the UN health body.

Since June last year, as many as 35 people have died and over 175 others have been infected with the JE virus that has spread to 117 local units in 45 districts of Nepal.

In 2024, a total of 23 people, including one in Kathmandu Valley, died of JE in Nepal, and over 80 were infected.

Health officials in Nawalparasi East said that 15 people were infected with the deadly virus in the district in the ongoing fiscal year, and six of them died from the severity of the infection.

Officials said that the vaccination programme was launched from the government’s own budget and Nawalparasi East was selected, as JE infection and death rate in the district was extremely high. The plan was to inoculate over 150,000 people above 35 years of age, but only 108,734 people were vaccinated until Saturday, according to them.

“Had we been able to vaccinate the vulnerable population in other districts, we could have saved more lives and prevented health consequences,” said Gautam. “But we don’t have enough vaccine doses for other districts.”

Health officials say their attempts to persuade development partners, including the World Health Organisation, to support a mass JE vaccination campaign have not succeeded.

Vaccination in Nawalparasi East was therefore launched using the health ministry’s own funds.

Both severity and death rates are very high among the unvaccinated population. Data show that 76 percent of JE-related deaths occurred among people above 40 years of age, who had not received the vaccine.

Health authorities have been administering the JE vaccine through the routine immunisation programme for the last two decades. All children under 15 years of age had already been vaccinated before the vaccine was included on the routine immunisation list.

Experts say the number of reported cases could be just the tip of the iceberg, as tests are usually carried out only on hospitalised patients with severe conditions.

They say that complications from JE infection can cause permanent injuries to the brain and the nervous system. As there is no specific cure, treatment focusses on managing symptoms. However, safe and effective vaccines have been developed to prevent infection.

In 2005, JE killed nearly 2,000 people in Nepal—mostly children in districts in the southern plains. Nepal started administering the vaccine in 2006, eight years before the World Health Organisation officially issued prequalification certification, due to high rates of infection and deaths from the virus at the time.

In the first phase, all populations of the highly affected four districts—Banke, Bardiya, Dang, and Kailali—were vaccinated. Later, the programme was expanded to 19 other affected districts, targeting children under 15.

The government integrated the JE vaccine into routine immunisation in 2015. Even then, people continue to die, and dozens get infected every year.

The JE virus is transmitted to humans through the bite of infected Culex mosquitoes. Pigs and ducks are considered natural reservoirs of the virus.

An estimated 12.5 million people are thought to be at high risk of JE infection in Nepal.