Japanese encephalitis: Be alert, not alarmed

Experts are asking people to be alert not alarmed as Japanese encephalitis virus (JEV) starts circulating in the community.

JEV is a viral illness spread to humans and other animals via mosquitoes. It has previously only been detected in northern parts of Australia but has recently been detected in NSW, Victoria, Queensland, and South Australia.

In most cases, JEV is very mild and causes few, or no, symptoms, but in around 1% of cases the virus can infect the brain or spinal cord. 

In these severe cases, the mosquito-borne virus can cause neurological illness with headache, convulsions and reduced consciousness, and in some cases death. Children under five years of age may be at risk of more severe outcomes with neurological illness. 

Unfortunately, the virus also has no specific treatment, but excellent supportive care that is available in Australia does improve outcomes

While JEV can be deadly, A/Prof Phil Britton, Staff Specialist in Infectious Diseases, says people don’t need to panic.

"We want people to be aware, not alarmed, and to do what they can to take responsibility for exposure to mosquitoes, "A/Prof Britton said.

"Most people who get infected from a mosquito actually don't become very unwell [and] might not get any symptoms."

“What we're really encouraging is for people to be super vigilant about how they use insect repellent, how they go out into the kinds of places where mosquitoes are prevalent, in camping and fishing and other sorts of activities.”

Simple actions to avoid mosquito bites include:

  • Avoid going outdoors during dawn and dusk when mosquitos are most active, especially close to wetland and bushland areas.
  • Wear long sleeves and pants outdoors (reduce skin exposure). Also wear shoes and socks where possible.
  • Apply repellent to all areas of exposed skin, especially those that contain DEET, picaridin, or oil of lemon eucalyptus. These are the most effective against mosquitoes. Always check the label for reapplication times*.
  • Protect infants less than three months old using an infant carrier draped with mosquito netting that is secured along the edges.
  • Reapply repellent after swimming. The duration of protection from repellent is also reduced with perspiration, such as during strenuous activity or hot weather so it may need to be reapplied more frequently.
  • Apply sunscreen first and then apply the repellent. Be aware that DEET-containing repellents may decrease the sun protection factor (SPF) of sunscreens so you may need to re-apply the sunscreen more frequently.
  • If camping, ensure the tent has fly screens to prevent mosquitoes entering.
  • Use mosquito coils and other devices that release insecticides when outside, in combination with topical insect repellents.
  • Reduce all water holding containers around the home where mosquitoes could breed. Mosquitoes only need a small amount of liquid to breed.

*Most skin repellents are safe for use on children aged three months and older when used according to directions, however some formulations are only recommended for children aged 12 months and older. Always check the product before using on a child.

Anyone with symptoms including fever, headache, confusion or seizures should seek medical attention, especially if they have been exposed to mosquitoes in at-risk areas, like the vicinity of the Murray River and its branches.

For further information on mosquito-borne disease and ways to protect yourself, visit the NSW Health website

See more fact sheets on specific mosquito-borne diseases, including Japanese encephalitis Ross River virus and Barmah Forest virus.