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Alert issued for mosquito-borne virus

March 14, 2022

What is Japanese encephalitis?

Japanese encephalitis is caused by the Japanese encephalitis virus (JEV). It is spread through mosquito bites and is more common in areas of increased mosquito activity. Infection in humans is most commonly asymptomatic, but on rare occasions it can result in severe disease and even death. It cannot be transmitted from human to human, or by eating meat from an infected animal.


Most cases of Japanese encephalitis in people are asymptomatic, however those with severe infection may experience: neck stiffness, coma, and more rarely, permanent neurological complications or death.

Encephalitis is the most serious clinical consequence of a JEV infection.

Illness usually begins with symptoms such as:

  • sudden onset of fever
  • headache
  • vomiting.

If you believe you may be infected with the Japanese encephalitis virus, seek urgent medical assistance.


There are 2 ways to prevent Japanese encephalitis:

  1. receiving a vaccination for the virus
  2. avoiding being bitten by mosquitos.

You can protect yourself from being bitten by mosquitos by:

  • applying and regularly reapplying an effective insect repellent on exposed skin
  • wearing long, loose fitting clothing when outside
  • ensuring accommodation, including tents, are properly fitted with mosquito nettings or screens
  • using insecticide sprays, vapour dispensing units (indoors) and mosquito coils (outdoors) to clear rooms and repel mosquitoes from an area
  • covering all windows, doors, vents and other entrances with insect screens
  • removing any water-holding containers where mosquitoes may breed.

The best mosquito repellents contain diethyltoluamide (DEET), picaridin, or oil of lemon eucalyptus.


Communicable Diseases Network Australia (CDNA) jurisdictional representative group has prioritised the following groups for priority vaccination, utilising existing supply on hand in Australia:

  • people who work at, reside at, or have a planned non-deferable visit to a:
    • piggery, including but not limited to farm workers and their families (including children aged 2 months and older) living at the piggery, transport workers, veterinarians and others involved in the care of pigs
    • pork abattoir or pork rendering plant
  • personnel who 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 (urban and remote)
    • entomologists
  • all 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.

Contact your local public health authority to find out if you should have a JEV vaccine.

JEV vaccine for travellers to Asia and the Torres Strait

We recommend vaccination against this disease if you are travelling to Asia and the Torres Strait region of Australia and will be:

  • travelling in rural areas
  • undertaking certain activities with increased risk of exposure
  • spending a month or more in the region.

You should avoid mosquito bites when you are in these areas.

People who work with animals in Australia may also choose to be vaccinated against this disease.


Japanese encephalitis is confirmed through a combination laboratory testing and clinical assessment.

If you think you may be infected with the Japanese encephalitis virus seek urgent seek medical assistance.


There are no treatments for Japanese encephalitis. You can relieve the symptoms by:

  • getting plenty of rest
  • drinking plenty of fluids
  • taking paracetamol for pain or fever.

In more severe cases, hospitalisation for supportive care and close observation may be required.