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Japanese encephalitis

Japanese encephalitis (JE) is a viral brain infection caused by the
Japanese encephalitis virus (JEV).1

Areas of risk

map chikungunya

JE is most common in rural areas
in Southeast Asia, the Pacific
Islands, and the Far East1

However, the risk for transmission may shift as boundaries between rural and urban areas are blurred. Recent cases of JE in US travelers visiting Asia occurred in urban and peri-urban regions.2

Recent JE outbreaks have been reported in Australia

As of January 2023, 7 deaths have been attributed to JE. The outbreak has officially been declared a Communicable Disease Incident of National Significance (CDINS) by the Australian government.3

Key facts

Japanese encephalitis is the leading cause of vaccine-preventable encephalitis in Asia.4

Many countries include JE vaccination as a part of a national immunization schedule.5

Up to 20,400 people die from JE every year.6,7

prevention guidance

More than one-third of people who traveled to Asia and developed JE were on short-term trips.8

The consequences of symptomatic JE are serious9,10

Up to 50% of JE survivors suffer from neurological, cognitive, and/or physical disabilities

About 30% of those who experience symptoms die

Only 19% of symptomatic patients fully recover

JE at a glance

Primary vector11,12

Culex, particularly Culex tritaeniorhynchus

Biting habits:

  • Evening to morning

Symptoms13,14

Most common:

  • Fever
  • Headache
  • Vomiting

Other:

  • Mental status changes
  • Neurologic symptoms
  • Weakness
  • Movement disorders
  • Seizures

Available treatment

None

Prevention15

Protective measures in accordance with CDC recommendations
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References: 1. Japanese encephalitis. National Health Service. Updated February 1, 2022. Accessed March 13, 2023. https://www.nhs.uk/conditions/japanese-encephalitis/ 2. Connor BA, Bunn WB. The changing risk of Japanese encephalitis for business travelers. Workplace Health & Safety. 2015;63(12):568. 3. Japanese encephalitis (JEV). Australian government. Department of Health and Aged Care. Updated February 28, 2023. Accessed March 13, 2023. https://www.health.gov.au/health-alerts/japanese-encephalitis-virus-jev/japanese-encephalitis-virus-jev 4. Japanese encephalitis virus. Centers for Disease Control and Prevention. Updated December 7, 2022. Accessed March 13, 2023. https://www.cdc.gov/japaneseencephalitis/index.html 5. Vaccination schedule for Japanese encephalitis. World Health Organization. Accessed March 13, 2023. https://immunizationdata.who.int/pages/schedule-by-disease/japenc.html 6. Japanese encephalitis. World Health Organization. Updated May 9, 2019. Accessed March 13, 2023. https://www.who.int/news-room/fact-sheets/detail/japanese-encephalitis 7. Singh LS, Singh HL, Thokchom L, et al. A descriptive study on prevalence pattern of Japanese encephalitis in State of Manipur. Indian J Med Microbiol. 2019;37(2):235-240. doi:10.4103/ijmm.IJMM_18_180 8. Pavli A, Maltezou HC. Travel-acquired Japanese encephalitis and vaccination considerations. J Infect Dev Ctries. 2015;9(9):917-924. doi:10.3855/jidc.5108 9. Hills SL, Walter EB, Atmar RL, Fischer M. Japanese encephalitis vaccine: recommendations of the Advisory Committee on Immunization Practices. MMWR Recomm Rep. 2019;68(2):1–33. doi:10.15585/mmwr.rr6802a1 10. Solomon T, Dung NM, Kneen R, et al. Seizures and raised intracranial pressure in Vietnamese patients with Japanese encephalitis. Brain. 2002;125(Pt 5):1084-1093. doi:10.1093/brain/awf116 11. Transmission of Japanese encephalitis virus. Japanese encephalitis virus. Centers for Disease Control and Prevention. Updated December 7, 2022. Accessed March 13, 2023. https://www.cdc.gov/japaneseencephalitis/transmission/index.html 12. Mosquito bite prevention (United States). Centers for Disease Control and Prevention. October 13, 2016. Accessed March 13, 2023. https://www.cdc.gov/chikungunya/pdfs/fs_mosquito_bite_prevention_us.pdf 13. Symptoms & treatment. Japanese encephalitis virus. Centers for Disease Control and Prevention. Updated October 13, 2022. Accessed March 13, 2023. https://www.cdc.gov/japaneseencephalitis/symptoms/index.html 14. Clinical and laboratory evaluation. Japanese encephalitis virus. Centers for Disease Control and Prevention. Updated February 8, 2019. Accessed March 13, 2023. https://www.cdc.gov/japaneseencephalitis/healthcareproviders/healthcareproviders-clinlabeval.html 15. Prevention. Japanese encephalitis virus. Centers for Disease Control and Prevention. Updated December 7, 2020. Accessed March 13, 2023. https://www.cdc.gov/japaneseencephalitis/prevention/index.html