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Japanese Encephalitis

a.k.a Jen

A deadly virus which infects travellers across Asia through mosquito bites. It can cause long term mental and physical disabilities, with very limited or no treatment options.

Key Fact

Around a third of people who have severe Japanese encephalitis suffer from long-term complications.1

disease risk map

How do people catch the disease?

When they’re bitten by infected mosquitoes which carry the virus.1

Which countries are affected?

Asian countries from India to Japan (see map). The risk is greater in rural areas.2

What are the symptoms?

Fever, chills, headache, muscle pain, mental confusion, spasms in the neck and spine and muscle weakness.1

How serious is the disease?

For almost all people who have the virus, the flu-like symptoms pass quickly. In rare cases, encephalitis develops when the virus spreads to the brain. This may cause fatal damage.1

People who survive severe encephalitis can end up with a long-term disability.

Can I reduce the chances of catching the disease?

You can take the following precautions to help reduce your risk of infection:

  • Visit your nearest convenient pharmacy or specialist travel health clinic for a risk assessment before your trip
  • Take steps to avoid mosquito bites when mosquitoes are most active (from dusk till dawn)3
  • Use a recommended insect repellent containing either 20% Picaridin (e.g Moskito Guard®), DEET or PMD4
  • Wear appropriate clothing (e.g long-sleeved clothes and long trousers)3


1. World Health Organization. Weekly Epidemiological Record. WHO Position Paper on Japanese Encephalitis. February 2015. Available online: http://www.who.int/wer/2015/wer9009.pdf (Last accessed September 2017)

2. Centers for Disease Control and Prevention. Yellow Book 2018. Chapter 3 Infectious Diseases Related to Travel. Japanese Encephalitis. May 2017. Available online: https://wwwnc.cdc.gov/travel/yellowbook/2018/infectious-diseases-related-to-travel/japanese-encephalitis (Last accessed September 2017)

3. Centers for Disease Control and Prevention. Yellow Book 2018. Chapter 2 The Pre-Travel Consultation. Counseling & Advice for Travelers. Protection against Mosquitoes, Ticks, & Other Arthropods. May 2017. Available online: https://wwwnc.cdc.gov/travel/yellowbook/2018/the-pre-travel-consultation/protection-against-mosquitoes-ticks-other-arthropods (Last accessed September 2017)

4. Public Health England. Mosquito bite avoidance for travellers. August 2017. Available online: https://www.gov.uk/government/publications/mosquito-bite-avoidance-for-travellers (Last accessed September 2017)


UK/TRA/0817/0171b September 2017