All people aged 30 and above in Madi Municipality and ward 19 of Bharatpur Metropolitan City in Chitwan district will be vaccinated against Japanese encephalitis (JE), as health authorities have prioritised these areas amid rising infections.

Last month, authorities administered the JE vaccine to everyone aged 35 and above in neighbouring Nawalparasi East, the district most affected by the virus in Nepal this fiscal year.

“We have selected the districts and local bodies based on risk assessment. We have focussed on areas with high morbidity and mortality rates, " said Dr Abhiyan Gautam, chief of the Immunisation Section at the Family Welfare Division under the Department of Health Services. “Due to a lack of vaccine doses and funds to purchase them, we are forced to be selective.”

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 infected and leaves up to half of survivors with severe lifelong disabilities, according to the UN health body.

Since June last year, 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 have been infected with the deadly virus in the district in the ongoing fiscal year [which started in mid-July 2025], and six of them died from the severity of the infection.

Chitwan is another district which also has a high morbidity and mortality rate. According to the Ministry of Health and Population, 15 people tested positive for JE in Chitwan since June last year, and five of them died.

Vaccination will start from April 8 in affected local units in Chitwan.

Officials said that the JE vaccine doses were purchased from the government’s own budget for Nawalparasi East, targeting 150,000 people aged 35 and above. However, only around 127,000 people received the vaccine. The remaining doses will now be administered to people aged 30 and above in Madi Municipality and ward 19 of Bharatpur Metropolis.

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

The Health Ministry's efforts to obtain JE vaccines from aid agencies, including the World Health Organisation, for a mass vaccination campaign were unsuccessful.

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 government’s routine immunisation list.

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

Complications from JE infection can cause permanent injuries to the brain and the nervous system, according to doctors. As there is no specific cure, treatment focuses 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 in the four highly affected 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.