Japanese Encephalitis virus

What is Japanese Encephalitis virus?

• Japanese encephalitis is a rare but potentially serious infection of the brain caused by the Japanese encephalitis virus (JEV).
• JEV is a nationally notifiable disease.
• JEV is spread by some types of mosquitoes and is more common in areas of increased mosquito activity. Pigs and certain water birds are hosts for the virus. There is no evidence of person-to-person transmission.
• Most people infected with JEV have no symptoms. Very rarely, brain inflammation (encephalitis) can occur.
• In March 2022, JEV was declared a Communicable Disease Incident of National Significance (CDINS) in Australia due to an increase in cases, and associated deaths, across multiple states in south-eastern Australia where JEV had not been previously detected. This CDINS was stood down in mid-2023, in recognition of the reduced risk and states and territories being well placed to continue to manage any ongoing risk.
• JEV encephalitis is a vaccine preventable disease. Two safe and effective vaccines are available in Australia. These vaccines have different recommendations depending on age, pregnancy, and immunocompromise.
• People can protect themselves against mosquito-borne illnesses by taking steps to limit exposure to mosquitos.
• Overseas travellers to endemic areas and those who live or work on the outer islands of the Torres Strait remain eligible for private vaccine.
• Additionally, in response to the 2022 outbreak, the Tasmanian Department of Health has implemented a JEV vaccination program (see Eligibility for the Department of Health JEV vaccination program 2024-25)

Symptoms 

• Less than 1% of people infected with JEV experience some symptoms. These typically include fever, joint pain, and rash.
• More rarely, this infection can progress to brain inflammation (encephalitis). 
• Children under 5 and older adults are at higher risk of developing severe illness.
• Symptoms of encephalitis may include:
  • headache
  • nausea and vomiting
  • confusion or change in mental status
  • generalised weakness
  • weakness on one side of the body or face
  • speech, visual or hearing problems
  • loss of coordination
  • seizures
  • coma
• Symptoms usually develop 5 to 15 days after a person has been bitten by an infected mosquito.

• If you experience these symptoms, seek medical attention immediately.

   

• In 2022, cases of JEV were detected in south-eastern Australia, where JEV had not been previously detected. All cases had extensive exposure to mosquitos or water-based activities prior to their illness onset, particularly along the Murray River at the border of NSW and VIC.  
• No cases have been detected in Tasmania. 
• The risk of being infected with JEV in Tasmania is currently assessed as very low.

How is it diagnosed?

• Clinical history, examination, and time spent in an area where JEV has been detected may lead a doctor to suspect JEV.
• Depending on the severity of the illness, JEV can be diagnosed either by a General Practitioner or in hospital.
• The diagnosis can be confirmed by laboratory testing of blood, or cerebrospinal fluid (the fluid surrounding the brain and spinal cord) collected through a lumbar puncture procedure.
• Other illnesses with similar symptoms may need to be ruled out.

How is it treated?

• There is no specific treatment for JEV infection.
• For people who experience symptoms, treatment aims to ease the discomfort of milder symptoms such as joint pain and fever.
• If your symptoms are severe or you experience complications, you may need to be treated in hospital.

How is JEV spread?

• JEV is spread by some types of mosquitoes.
• There is no evidence of person-to-person transmission.
• Pigs and certain water birds can also be infected with JEV. While they cannot directly transfer the virus to humans, indirect transmission can occur via mosquitoes.

Where is it found in Tasmania?

• No cases have been detected in Tasmania.
• The risk of being infected with JEV in Tasmania is currently assessed as very low.

How can JEV be prevented?

• You can reduce your chances of becoming unwell with JEV by:
  • Protecting yourself against mosquito bites
  • Receiving a JEV vaccine
• You can prevent JEV and other mosquito-borne illnesses by avoiding mosquito bites through the following actions:
  • Avoid known mosquito-infested areas, where possible
  • Try to limit outdoor activity if many mosquitoes are about
  • Take extra care during peak mosquito-biting hours, especially around dawn and dusk and when outdoors or camping
  • Wear covered footwear and loose-fitting, light-coloured clothing that covers as much of your body as possible. Mosquitoes can bite through tight-fitting clothing.
  • Use insect repellents containing DEET (Diethyl toluamide) picardin or on all exposed skin. Always read the manufacturer’s instructions before applying it.
  • Use ‘knockdown’ fly sprays and plug-in repellent devices indoors
  • Use mosquito coils outdoors in areas where you gather to sit or eat
  • Remove potential mosquito breeding sites from around the home (e.g., containers that collect water)
• Use insect screens on your house, caravan, or tent. If this is not possible, use a mosquito net.

Vaccination information

• There are two JEV vaccines available in Australia (Imojev and JEspect). Both are safe and effective for preventing JEV.
• JEV vaccination is recommended and available on private prescription for overseas travellers to endemic areas and those who live or work on the outer islands of the Torres Strait. 
• In response to the 2022 south-eastern Australian outbreak, a state-funded vaccination program is available for eligible people (see Eligibility for the Department of Health JEV vaccination program 2024-25)
• Visit your GP, travel doctor or another immunisation provider for more information.

Where to get help

• In an emergency call ‘000’ (triple zero) for an ambulance
• You can also present to the emergency department of your nearest hospital or speak to your General Practitioner.
• For other queries, contact the Communicable Diseases Prevention Unit on 1800 671 738 (option 3 to speak to a Communicable Diseases Clinical Nurse Consultant) or via fax (6173 0821).

JEV Vaccine information for health professionals

• Imojev is a live attenuated vaccine given subcutaneously as a single dose. It is suitable for people aged ≥9 months where there are no contraindications to its use. Imojev is contraindicated in those who are pregnant, planning pregnancy (avoid pregnancy for 28 days), and immunocompromised. It is not licensed for use in children <9 months of age.
• JEspect (branded Ixiaro) is an inactivated vaccine given intramuscularly in a two-dose schedule. It is recommended for pregnant and breastfeeding people, children aged 2 months to <9 months, and immunocompromised individuals. The recommended doses vary with age. The dose interval is 28 days although can be reduced to 7 days if there is a high risk of exposure.
• Both vaccines can be co-administered with other vaccines if required.
• Adverse events are generally minor and short-lived, with most symptoms resolving within a few days.
• More detailed information on the vaccines can be found on the ATAGI clinical guidance and Australian Immunisation Handbook webpages.

Eligibility for the Department of Health JEV vaccination program 2022-2025

• The Communicable Diseases Network of Australia (CDNA) has prioritised certain risk groups for JEV vaccination in response to the 2022 outbreak.
• As the risk of JEV within Tasmania is assessed as very low, only people travelling to or residing on mainland Australia, or the Torres Strait and Tiwi Islands and who meet one of the following criteria are eligible for vaccination:
  • work at or reside at a piggery, including but not limited to farm workers and their families (including children aged 2 months and older), transport workers, veterinarians and others involved in the care of pigs
  • work at or reside at a pork abattoir or pork rendering plant
  • work directly with mosquitoes through their surveillance (field or laboratory based) or control and management, and indirectly through management of vertebrate mosquito-borne disease surveillance systems (e.g. sentinel animals) such as environmental health officers and workers and entomologists
  • diagnostic and research laboratory workers who may be exposed to the virus, such as persons working with JEV cultures or mosquitoes with the potential to transmit JEV; as per the Australian Immunisation Handbook.
  • living near a piggery with current or recent JEV activity
  • feral pig hunters and doggers
  • individuals living, working, or undertaking frequent recreational activities in regions, including aquatic habitats, determined to be at current or anticipated, near future JEV risk
• If you have patients who meet the above criteria, please contact the Communicable Diseases Prevention Unit (CDPU) Immunisation team to discuss their eligibility. CDPU will undertake a risk assessment based on the epidemiology of JEV in Australia.
• Health professionals can contact the CDPU Immunisation team on 1800 671 738 (option 3 to speak to a Communicable Diseases Clinical Nurse Consultant) or via fax (03) 6173 0821.
• Additionally, overseas travellers to endemic areas and those who live or work on the outer islands of the Torres Strait continue to be recommended to receive private vaccine.

How much does it cost?

• The vaccine will be free of charge for those deemed eligible.
• Note, people who request JEV vaccine for domestic and international travel purposes are not eligible for a free vaccine under this public health program and instead should visit their GP, travel doctor or another immunisation provider.

Further Information

• Japanese encephalitis on the Australian Government Department of Health website.
• Information about Japanese encephalitis disease, vaccines and recommendations for vaccination from the Australian Immunisation Handbook

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