What is Japanese encephalitis?

Japanese encephalitis is an infection that can affect the central nervous system and cause serious complications and even death.

It is endemic (regularly found) in parts of Asia and the Torres Strait.

Japanese encephalitis outbreaks in Australia

Before 2021, there were only 5 recorded cases of Japanese encephalitis acquired in mainland Australia. All of these were in Northern Australia. No locally acquired cases had been detected since 1998.

Between January 2021 and February 2023, 45 people in mainland Australia were diagnosed with Japanese encephalitis. During this outbreak, 7 people died. Cases were found as far south as Victoria.

An emergency response to this outbreak involved:

• vaccinating people at high risk
• raising public awareness of Japanese encephalitis

The end of the emergency response to Japanese encephalitis in Australia was announced in June 2023.

What are the symptoms of Japanese encephalitis?

Most people infected with the Japanese encephalitis virus don't experience any symptoms.

If you do get symptoms, you are likely to notice them about 5 to 15 days after being bitten by an infected mosquito.

The Japanese encephalitis virus can cause encephalitis and meningitis. These conditions are serious, and can cause symptoms such as:

• fever
• vomiting
• headache and neck stiffness
• convulsions and seizures (fits)
• muscle weakness and paralysis
• fatigue
• coma and brain damage

Japanese encephalitis can also make you feel confused or agitated.

What causes Japanese encephalitis?

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

Japanese encephalitis only spreads to humans via bites from infected mosquitoes.

Animals such as pigs, waterbirds and horses can also catch Japanese encephalitis. These animals can't transfer the virus to humans. If you work closely with these animals — especially pigs — you're at increased risk of being bitten by an infected mosquito.

You cannot catch Japanese encephalitis:

• through contact with infected people
• by eating meat from an infected animal

When should I see my doctor?

If you have recently been in an area with reports of Japanese encephalitis virus, and you experience sudden symptoms, seek urgent medical attention.

If you think you may have Japanese encephalitis, visit your nearest emergency department or call an ambulance on triple zero (000).

How is Japanese encephalitis diagnosed?

Your doctor can diagnose Japanese encephalitis by asking you about your symptoms. They may also ask if you have recently travelled to any areas where there are cases of JEV.

If your doctor thinks you have Japanese encephalitis, further tests can confirm your diagnosis. These may include a:

• blood test
• lumbar puncture (spinal tap)

Japanese encephalitis is a nationally notifiable disease in Australia. This means, if you are diagnosed with Japanese encephalitis, your doctor will let your local public health authority know. They will check who you have been in contact with and take steps to control an outbreak.

How is Japanese encephalitis treated?

There is no specific medicine or treatment for Japanese encephalitis.

If you have symptoms of Japanese encephalitis, you will likely need treatment in hospital to manage:

• seizures
• encephalitis
• meningitis

Antibiotics will not help you recover because this illness is caused by a virus, not bacteria.

Can Japanese encephalitis be prevented?

The 2 best ways to prevent Japanese encephalitis are to:

1. avoid being bitten by mosquitoes, especially in areas where the virus is common
2. get vaccinated against Japanese encephalitis virus

What are the recommendations for the Japanese encephalitis virus vaccine?

Vaccination is a safe and effective way to reduce your chance of catching Japanese encephalitis.

Vaccination is recommended for people who:

• spend a month or more in Asia or the Torres Strait region of Australia during the wet season
• work in laboratories with Japanese encephalitis virus
• work with mosquitoes
• work with pigs

See below for details about the Japanese encephalitis vaccination.

You can talk to your doctor about which vaccine is best for you or your child.

If you're not sure whether you should get vaccinated, you can ask your:

• doctor
• travel clinic

How can mosquito bites be avoided?

To protect yourself from mosquito bites, you can try these things:

• Reduce skin exposure and avoid tight clothes. Instead, wear loose-fitting clothes such as long-sleeved shirts, long pants, long socks and enclosed footwear.
• Avoid spending time outside at dawn or dusk, as this is when mosquitoes are most active.
• Use insect repellent. Choose products that contain diethyltoluamide (DEET), picaridin or lemon eucalyptus oil — these are most effective against mosquitoes.
• Stay in rooms that have flyscreens over the doors and windows.
• Sleep in rooms that have mosquito nets.
• Don't leave water containers open — mosquitoes breed in still water.

You can find out more about insect bites here.

What are the complications of Japanese encephalitis?

Japanese encephalitis can cause severe complications or death. Complications of Japanese encephalitis include permanent injury to your brain or nervous system.

About half of the people who survive symptomatic Japanese encephalitis experience complications.

Resources and support

You can visit the Department of Health and Aged Care for more information about Japanese encephalitis.

For information on where you live, visit your state or territory's website:

• Australian Capital Territory
• New South Wales
• Northern Territory
• Queensland
• South Australia
• Tasmania
• Victoria
• Western Australia

For more information on staying safe from Japanese encephalitis while travelling, you can:

• check the Smartraveller website
• read more about travel vaccinations

If you need advice on Japanese encephalitis, call healthdirect on 1800 022 222 to speak with a registered nurse, 24 hours, 7 days a week (known as NURSE-ON-CALL in Victoria).

Languages other than English

The Department of Health, Disability and Ageing has Japanese encephalitis resources in many community languages.

The Northern Territory Government also offers Japanese encephalitis information in other languages.

Information for Aboriginal and/or Torres Strait Islander peoples

The Department of Health, Disability and Ageing has Japanese encephalitis resources for Aboriginal and/or Torres Strait Islander people.