Japanese encephalitis

Japanese encephalitis (JE) is caused by the Japanese encephalitis virus.

Encephalitis is inflammation of the brain tissue and is usually caused by an infection.

The virus is spread through mosquito bites.

Infection in humans is most commonly asymptomatic. On rare occasions, it can result in severe disease with brain damage and even death.

How it is spread

JE is spread by the bite of an infected mosquito. It cannot be spread from person to person.

In countries or regions where the virus is present, the transmission is more common in areas of increased mosquito activity.

Pigs and wild water birds help spread the virus. It multiplies in infected pigs, leading to very high levels in their blood. Mosquitoes feeding on infected pigs and water birds pick up the virus and may spread it to humans.

Where and when the virus is found

The virus has been found throughout Asia and Australia.

The NT has recorded 3 cases of JE in humans:

  • The NT’s first confirmed case was recorded in February 2021 in the Tiwi Islands, when a woman died after contracting the virus.
  • The second case is a Victorian man in his 70s who contracted the virus while travelling in the Top End region in May 2021. He has since recovered.
  • The third case is a child from a remote community in the Top End who became unwell in June 2022. The child has made a good recovery.

For information about JE cases across Australia, go to the Australian Government's Health website.


It usually takes 5 to 15 days between getting bitten by the infected mosquito and becoming unwell.

Symptoms include:

  • headaches
  • fever
  • seizures or fits (especially in young children)
  • neck stiffness
  • drowsiness
  • confusion, delirium and coma in severe cases.


There are no specific treatments for JE.

In most cases, individuals are admitted to hospital where they are closely observed and given supportive care.

How to protect yourself

There are 2 ways to prevent JE:

  • avoid being bitten by mosquitoes
  • vaccination.

Find out how to protect yourself by watching the video below.

Avoid mosquito bites

You can protect yourself from being bitten by mosquitoes by doing the following:

  • Avoid areas with numerous mosquitoes close to wetlands where birds and feral pigs might be present.
  • Wear protective clothing outdoors to cover feet, legs, and arms. Loose, light-coloured clothing is best.
  • Avoid being outside when mosquitoes are most active. This happens just before sunset and the following hour, during the night and early in the morning.
  • Use personal protective repellents containing diethyl toluaminde (DEET), picaridin or PMD (extract of lemon eucalypt) on areas of exposed skin.
  • Make sure infants and children are adequately protected against mosquito bites.
  • Use mosquito coils, candle heated or gas operated devices with insecticide treated pads in sheltered or low wind outdoor areas.
  • Make sure fly-screens in houses or caravans are in good condition
  • If camping, sleep in a mosquito-proof tent or under a mosquito net.

Repellents only protect against mosquito bites for up to 4 hours, not all night.

To prevent mosquito borne disease, read more about protecting yourself from mosquitoes.


JE is a vaccine-preventable disease. Across Australia, JE vaccine supply is currently limited. Therefore, a vaccine at this time is recommended for certain people at highest risk of infection.

In the NT, these are people who:

  • work directly with mosquitoes or feral pigs through surveillance or control and management, such as:
    • environmental health officers and workers
    • entomologists
    • vets
    • rangers
  • live within 10km of a positive human case
  • live in a high risk remote area.

NT Health is working to vaccinate these groups and will contact those who are eligible.

Read more about JE vaccines on the Australian Government's Health website.


For more information about mosquitoes and virus ecology, contact your nearest Centre for Disease Control or go to the Department of Health website.

For biosecurity alerts and updates, go to the Biosecurity NT Facebook page.

Last updated: 16 September 2022

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