Japanese encephalitis is caused by the Japanese encephalitis virus (JEV), which is spread through mosquito bites and is more common in areas of increased mosquito activity.
It is a rare but potentially serious infection of the brain. 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.
Who is at risk?
There may be an increased risk of transmission near the border of Victoria and New South Wales, where both JEV infections in pigs have been identified and where the human suspected cases had spent time prior to becoming unwell.
Anyone is potentially at risk of being bitten by mosquitoes and while most bites will only cause minor swelling and irritation, an infected mosquito can transmit potentially serious diseases. This risk may be increased particularly near the Murray River and its surrounds, from Mildura to Wodonga, where increased mosquito numbers have been detected recently. People with increased exposure to mosquitoes may be at a higher risk of infection, particularly people camping, or working or spending time outdoors in these regions.
People who work with or are in contact with pigs may also be at increased risk of infection. Children aged under 5 years old and older people who are infected with JEV are at a higher risk of developing more severe illness, such as encephalitis.
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
If you believe you may be infected with the Japanese encephalitis virus, seek urgent medical assistance.
How it spreads
The Japanese encephalitis virus spreads when a human is bitten by a mosquito that has previously bitten an animal infected with the virus.
You can help stop the disease spreading by avoiding being bitten by mosquitos.
People and horses are considered ‘dead end’ hosts - once infected, they do not play a role in transmitting the virus.
There are two ways to prevent Japanese encephalitis:
- receiving a vaccination for the virus
- 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.
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.
A vaccination program targeting those most at risk will commence shortly.
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.