Japanese encephalitis

Encephalitis is inflammation of the brain tissue and is usually caused by an infection. Japanese encephalitis (JE) is a potentially fatal disease caused by the Japanese encephalitis virus.

How it is spread

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

Pigs and wild water birds play an important role in the spread of JE virus.  The virus multiplies in infected pigs, leading to very high levels in their blood.  Mosquitoes feeding on infected pigs are highly likely to pick up the virus and may then spread it to humans.  

Where and when the virus is found

JE virus has been found throughout Asia and in the Torres Strait region of Australia. To date no cases have been acquired in the Northern Territory (NT).

In 1995 the first case of JE in Australia was reported from Badu Island in the Torres Strait. The virus is thought to have spread south from Papua New Guinea.  Since 1995 there have been 5 cases (including 2 deaths) of JE acquired in Australia. Four of the cases have been acquired in the Torres Strait and one from the mainland on Cape York Peninsular.

The risk to humans is greatest during or just after the Wet season when large numbers of the common banded mosquito are present. Humid conditions allow mosquitoes to live longer, which provides more chance for a mosquito to pick up the virus from an animal and live long enough to pass it on to humans.

The virus has not been found in the NT however the mosquitoes capable of spreading the virus are found in the NT.

How serious is JE

JE is a potentially fatal disease, however only 1 in 30-300 people bitten by an infected mosquito will become ill.

Of people who develop the disease, 10 to 30% will die, 50% will recover but have permanent disability and 25% will recover completely. Children under 15 years of age are at greatest risk of developing severe disease.


It usually takes 5 to 15 days between getting bitten and becoming unwell.

Symptoms include: headaches, fever, seizures or fits (especially in young children), neck stiffness, drowsiness, confusion and progression to delirium and coma in severe cases.


There is no specific treatment for JE disease.



A JE vaccine is available and is recommended for:

  • travellers spending 1 month or more in rural areas of Papua New Guinea, East Timor or Asia, particularly if travel is during the wet season, and/or there is considerable outdoor activity and/or the standard of accommodation is suboptimal
  • travellers spending a year or more in Asia (except Singapore), even if most of the stay is in urban areas
  • all residents (over 1 year of age) of the outer islands in the Torres Strait
  • anyone who will be living or working on the outer islands of the Torres Strait for a cumulative total of 30 days or more during the wet season (December to May).

Personal protective measures

You can help protect yourself against JE by doing the following:

  • avoid being outside when vector mosquitoes are most active, from just before and until 2 hours after sunset
  • wear loose light coloured clothing with long sleeves, long trousers and socks (mosquitoes can bite through tight-fitting clothes)
  • apply a protective repellent containing up to 20 percent diethyl toluaminde (DEET) or picaridin to exposed areas of skin (lotions and gels are more effective and long lasting than sprays)
  • after sundown avoid areas with numerous mosquitoes in close proximity to wet lands where birds and feral pigs might be present
  • ensure flyscreens in houses or caravans are in good repair
  • if camping out, either 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.

What is the risk in the NT

The JE virus has not been detected in the NT although the mosquitoes capable of spreading it are common. 

Medical Entomology conducts a flavivirus surveillance program to ensure early detection of any spread of JE virus into the NT.


For more information contact your nearest Centre for Disease Control.

For more information go to protecting yourself against mosquitoes.

Last updated: 12 May 2016

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