Japanese encephalitis

About Japanese encephalitis

Japanese encephalitis is a rare but potentially serious infection of the brain caused by the Japanese encephalitis virus. It can be spread to humans through mosquito bites.

Japanese encephalitis virus occurs in many parts of southern and eastern Asia, and in recent years has extended beyond its traditional boundaries to eastern Indonesia, Papua New Guinea and the Torres Strait. Japanese encephalitis is now considered endemic in the Torres Strait region.

In early 2022, Japanese encephalitis virus was detected in pigs in Victoria and several other Australian jurisdictions (New South Wales, Queensland, the Northern Territory and South Australia). Locally acquired human cases of Japanese encephalitis virus were subsequently confirmed.

Japanese encephalitis in Victoria

Japanese encephalitis virus was detected in Victoria for the first time in February 2022 in pigs, humans, and mosquitoes. A comprehensive response across human and animal health sectors has been implemented in Victoria following the first detections and is ongoing.

Human cases of Japanese encephalitis virus infection have been reported in Victoria, New South Wales, and South Australia. More information is available on the Department of Health’s Japanese Encephalitis page.

Who is at risk of Japanese encephalitis?

Anyone is potentially at risk of being bitten by mosquitoes. While most bites only cause minor swelling and irritation, an infected mosquito can potentially transmit Japanese encephalitis and other mosquito-borne diseases.

People who live, work or spend time outdoors in northern Victoria, particularly in inland riverine regions extending up towards the Murray River, may be at higher risk of Japanese encephalitis.

People who live or work at properties with pigs may also be at higher risk. If you work around pigs, please refer to the Agriculture Victoria website for more information.

Symptoms of Japanese encephalitis

Symptoms usually develop 5 to 15 days after being bitten by an infected mosquito.

Most people with Japanese encephalitis virus infection do not have symptoms or have only mild symptoms. A small number (about one in every 250 people) develop severe infection of the brain (encephalitis).

Some people may have symptoms such as:

• fever
• headache
• vomiting

People with severe infection may develop symptoms such as:

• severe headache
• neck or back stiffness
• sensitivity to light
• confusion
• seizures
• paralysis
• coma.

Encephalitis may lead to death or permanent disability.

Anyone experiencing these symptoms should seek urgent medical attention.

Transmission of Japanese encephalitis

Japanese encephalitis virus is spread to humans through the bite of an infected mosquito.

It cannot be spread directly from person to person.

Prevention of Japanese encephalitis

In Victoria, mosquitoes can transmit a number of other viruses that cause disease, including Ross River virus, Barmah Forest virus, Murray Valley encephalitis virus and Kunjin virus.

The most effective way to prevent Japanese encephalitis and other mosquito-borne diseases is by avoiding mosquito bites and removing mosquito breeding sites around your home and property.

How to protect yourself from mosquitoes

Protect yourself and your family from exposure to mosquitoes and mosquito-borne diseases:

• Cover up – wear long, loose-fitting, light-coloured clothing.
• Use mosquito repellents containing picaridin or DEET on all exposed skin.
• Limit outdoor activity if lots of mosquitoes are about.
• Remove stagnant water where mosquitoes can breed around your home or campsite.
• On holidays make sure your accommodation is fitted with mosquito netting or screens.
• Don’t forget the kids – always check the insect repellent label. On babies, you might need to spray or rub repellent on their clothes instead of their skin.

Avoid applying repellent to the hands of babies or young children.

• Use ‘knockdown’ fly sprays and plug-in repellent devices indoors.
• Sleep under mosquito nets treated with insecticides if you don’t have insect screens on windows on your home or are sleeping in an untreated tent or out in the open.
• Mosquito coils can be effective in small outdoor areas where you gather to sit or eat.
• Visit our Protect yourself from mosquito-borne disease page for more information.

Vaccination for Japanese encephalitis

A vaccine is available to protect against Japanese encephalitis. In Victoria, Japanese encephalitis vaccine is free-of-charge for eligible individuals, including those not eligible for Medicare. Please note, some providers may charge an administration or consultation fee. Be sure to check if this applies to you.

Supply of Japanese encephalitis vaccine continues to be limited in Australia. Nevertheless, people listed in the specific priority groups are advised to contact their doctor (GP), community pharmacy, Aboriginal health service, local council, or local public health unit for more information.

For more information and a full list of Japanese encephalitis vaccine eligibility criteria, see the Department of Health’s Japanese encephalitis page. Speak to your doctor (GP) or immunisation provider, who will assess your eligibility and offer you the free Japanese encephalitis vaccine if you are eligible.

Japanese encephalitis vaccine booster doses are recommended for some people one to 2 years after their primary course if they remain eligible in Victoria.

Speak with your doctor (GP) or immunisation provider if it has been one to 2 years since getting a primary course of Japanese encephalitis vaccine to check if you require a booster dose.

Side effects of Japanese encephalitis vaccines

Common side effects of Japanese encephalitis vaccines are:

• pain
• tenderness
• redness
• swelling at the injection site.

Fever may occur and is more common in children. Headache or muscle aches can also occur, mainly in adults. These side effects usually go away within a few days. Severe reactions to Japanese encephalitis vaccine are very rare.

If you are pregnant or breastfeeding and at risk of Japanese encephalitis infection, contact your GP (doctor) for further information.

Treatment for Japanese encephalitis

There is no specific treatment available for Japanese encephalitis. For people with symptoms, treatment aims to reduce the severity of the symptoms and may include medication and hospitalisation.

The best way to avoid infection is to avoid being bitten by mosquitoes.

Where to get help

• Always call an ambulance in an emergency (triple zero) Tel. 000
• Emergency department of your nearest hospital
• Your GP (doctor)
• Nurse-on-Call Tel. 1300 60 60 24 (24 hours, 7 days) – for confidential health advice from a registered nurse
• Your local council – for information about mosquito control programs in your area