Japanese Encephalitis

Japanese Encephalitis (JE) (update July 2023)

JE is a serious illness that affects the brain.  Although many people get infected with the JE virus without becoming ill, for those who do show symptoms, 1/3rd will recover, 1/3rd will die and 1/3rd will suffer serious brain damage.  The virus that causes JE is carried by culex mosquitoes which breed in flooded rice fields. Mosquitoes feed on infected pigs and wild birds, and infected mosquitoes transmit JE virus to humans and animals while feeding. The disease is inherently rural in nature. JE is endemic in the Terai, with maximum number of cases occurring in the western districts of Banke, Kanchanpur and Kailali. JE immunization with CD-JEVAX at 1 year of age is included in the national immunization program of Nepal with excellent results.

JE is firmly established in the Kathmandu valley with several cases each year being admitted to different area hospitals. There has been a single case report of JE in a traveler to Nepal in 2012.The highest risk months for JE are August, September and early October of each year.  This raises the question as to whether all residents and tourists to Kathmandu Valley should receive the vaccine against JE.

Short term travelers who will stay in Kathmandu for a few days who will go trekking are the lowest risk individuals and we do not feel that they need to be immunized against JE. Travelers who will reside in Kathmandu particularly in the post-monsoon months of August to early October are recommended to obtain the JE vaccine. Persons who will be living in known JE endemic areas such as most of the Terai and in Kathmandu should be immunized against JE.


Japanese Encephalitis (JE) Vaccines

CD.JEVAX, the live Chengdu SA-14-14-2 strain vaccine is the most widely used vaccine in Asia.  It is a very safe vaccine with no serious side effects like encephalitis or hypersensitivity reactions reported in over 300 million doses used. Single shot offers protection for up to 5 years however, a booster at one year is recommended for long term protection. Manufacturers recommend 2 shots one year apart when started at 9 month-1 year of age.


Inactivated Vero cell JE vaccine (JEEV, similar to Ixiaro in the West) is given as 2 injections, 28 days apart, and is approved for persons >1 year of age.

Since JE is transmitted by the bite of an infected mosquito, mosquito bite prevention measures are just as important to protect against this disease. The JE causing mosquitoes bite at dusk and at night time and it is important to sleep inside a treated mosquito net or in screened accommodation, wear long sleeved clothing and use an insect repellent e.g. 30% DEET.

Please come and speak with a nurse at CIWEC or write to us if you have questions about use of JE vaccines.