Japanese encephalitis (JE) is a serious illness that affects the brain. Many people infected with the JE virus never become ill — but of those who do develop symptoms, a third recover, a third die and a third are left with serious brain damage.
The virus is carried by Culex mosquitoes, which breed in flooded rice fields. Mosquitoes feed on infected pigs and wild birds, then pass the virus to humans and animals. The disease is essentially rural. JE immunization with CD-JEVAX at 1 year of age has been part of Nepal's national immunization program since 2006.
The disease has now shifted to older age groups: in 2026 there were 131 confirmed cases and 28 deaths in Nepal, with most deaths in people over 50. Vaccination campaigns have been carried out in the most affected districts, Jhapa and Kailali.
Risk in Kathmandu
JE has been confirmed in the Kathmandu valley, and there was a single case report of JE in a traveler to Nepal in 2012. The highest-risk months are August, September and October. This raises the question of whether all residents of and visitors to the valley should be vaccinated.
Who should be vaccinated?
- Short-term travelers staying in Kathmandu for a few days and going trekking are at the lowest risk. We don't feel they need JE vaccine.
- Travelers who will live in Kathmandu, particularly through the post-monsoon months of August to October, are recommended to get the vaccine.
- Everyone living in known JE-endemic areas — most of the Terai, and Kathmandu — should be immunized.
JE vaccines
Inactivated Vero cell JE vaccine (JEEV), similar to Ixiaro in the West, is given as two injections 28 days apart and is approved from 1 year of age. JEEV is available at CIWEC.
CD-JEVAX, the live Chengdu SA-14-14-2 strain vaccine, is the most widely used JE vaccine in Asia. A single shot protects for up to 5 years, but a booster at one year is recommended for long-term protection. When started at 9 months to 1 year of age, manufacturers recommend two shots a year apart. It is available only through the government program.
Avoiding mosquito bites
Because JE is spread by mosquito bites, bite prevention matters just as much as vaccination. JE mosquitoes bite at dusk and at night:
- Sleep under a treated mosquito net or in screened accommodation.
- Wear long-sleeved clothing.
- Use an insect repellent, such as 30% DEET.
Come and speak with a nurse at CIWEC, or write to us, if you have questions about JE vaccines.