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What is it

Japanese encephalitis is a viral disease transmitted by mosquitoes that may cause inflammation of the membranes around the brain.1

Japanese encephalitis occurs in almost all Asian countries and parts of the western Pacific. It is mainly a threat in rural agricultural areas where there is widespread irrigation (artificial watering of crops).2

Who is at risk

Travellers visiting rural Asia are at the highest risk, with children and those aged 65 and over most vulnerable. They have a higher risk of infection if they:

  • visit rural and agriculture areas, especially for an extended period of time (≥ 1 month)
  • Do outdoor activities (e.g. hiking, camping, cycling, fieldwork)2

What are the symptoms

Most infected people don’t develop any symptoms, but in those who do, the disease can be serious. Symptoms include the onset of high fever and headaches, which appear after five to fifteen days of incubation. Japanese encephalitis also affects the central nervous system, resulting in behavioural changes and movement disorders.3 Infants and the elderly who are infected are more likely to develop severe disease.2

Less than 1% of infected people develop encephalitis (brain swelling), which is fatal in about 20% to 30% of these cases.3

How is it spread

Japanese encephalitis is caused by a Flavivirus.
The disease spreads to humans when they are bitten by an infected mosquito.4

How is it prevented

Japanese encephalitis is a vaccine-preventable disease.5 Consult a healthcare provider or visit a travel health clinic preferably 6 weeks before you travel.6

It is recommended that the following travellers consider getting vaccinated:

  • those spending a month or more in a rural or urban area where Japanese encephalitis is present
  • those spending a large amount of time outdoors in a rural or urban area where Japanese encephalitis is present (even if living in the area for less than one month)

Most travellers going to countries where Japanese encephalitis occurs are at low risk. However, you can help prevent Japanese encephalitis by protecting yourself from mosquito bites, especially from sunset to sunrise.6

How is it treated

Japanese encephalitis is diagnosed based on symptoms and laboratory tests.7

There is no specific treatment for Japanese encephalitis. However, medical care can help you recover and help control symptoms.7 Medical advice is recommended for the onset of symptoms. For further information regarding Japanese encephalitis and immunization, please speak with your healthcare provider.


  1. WHO. Water-related diseases. Japanese Encephalitis. (2001) http://www.who.int/water_sanitation_health/diseases-risks/diseases/encephalitis/en/
  2. Government of Canada. Risks of Japanese Enchephalitis. (2016). https://www.canada.ca/en/public-health/services/diseases/japanese-encephalitis/risks-japanese-encephalitis.html
  3. Government of Canada. Symptoms of Japanese Enchephalitis. (2016). https://www.canada.ca/en/public-health/services/diseases/japanese-encephalitis/symptoms-japanese-encephalitis.html
  4. Government of Canada. Causes of Japanese Enchephalitis. (2016). https://www.canada.ca/en/public-health/services/diseases/japanese-encephalitis/causes-japanese-encephalitis.html
  5. Valneva Ixiario Product Monograph, (2017). https://pdf.hres.ca/dpd_pm/00039005.PDF
  6. Government of Canada. Prevention of Japanese Enchephalitis. (2016). https://www.canada.ca/en/public-health/services/diseases/japanese-encephalitis/prevention-japanese-encephalitis.html
  7. Government of Canada. Treatment of Japanese Enchephalitis. (2016). https://www.canada.ca/en/public-health/services/diseases/japanese-encephalitis/treatment-japanese-encephalitis.html