With the arrival of summer, NSW Health is urging people to protect themselves from mosquito bites after earlier than expected detections of two mosquito borne viruses that can cause brain swelling.
The first detection of Japanese Encephalitis virus in mosquitoes for the 2025-2026 season was detected last week in mosquitoes collected from the Horsham Rural City Council region in Victoria.
Another mosquito borne virus, Kunjin virus, has also been detected in Western NSW at Cowra, through a sentinel chicken blood sample on 20 November 2025 as part of NSW Health's routine surveillance.
NSW Health's Director Health Protection, Dr Stephen Conaty, said these detections so early in the summer season are concerning.
"Mosquito numbers will likely increase with warmer weather, and we remind everyone in NSW to protect themselves against mosquito bites, which can cause diseases such as Japanese Encephalitis and Murray Valley Encephalitis, and infection with Kunjin virus, Ross River virus and Barmah Forest virus," Dr Conaty said.
There are now 60 NSW LGAs that are considered to be higher risk of Japanese Encephalitis virus. Residents and travellers to these LGAs should take particular care to avoid mosquito bites.
"There is a safe, effective and free vaccine to protect against Japanese Encephalitis (JE). This vaccine is free to anyone who lives or routinely works in these 60 LGAs west of the dividing range and in northern NSW, and for people who work in some other high-risk occupations."
JE vaccine is available through General Practitioners, Aboriginal health services and pharmacists. People who meet the eligibility criteria should make an appointment ahead of time and let the provider know it is for the JE vaccine. These providers may require a few days' notice so they can order the vaccine and may charge a consultation fee.
A booster dose may be recommended for some people with ongoing risk of exposure, one to two years after completing their primary course.
Other than the JE vaccine, there is no vaccination or specific treatment for Kunjin virus or other mosquito borne diseases in Australia. The best way to avoid infection is to avoid being bitten by mosquitoes, which are more active between dusk and dawn.
To prevent mosquito bites:
- Apply repellent to exposed skin. Use repellents that contain DEET, picaridin, or oil of lemon eucalyptus. Check the label for reapplication times
- Re-apply repellent regularly, particularly after swimming. Be sure to apply sunscreen first and then apply repellent
- Wear light, loose-fitting long-sleeve shirts, long pants, socks and covered footwear
- Avoid going outdoors during peak mosquito times, especially dawn and dusk
- Use insecticide sprays, vapour dispensing units and mosquito coils to repel mosquitoes (mosquito coils should only be used outdoors in well-ventilated areas)
- Cover windows and doors with insect screens and checking there are no gaps
- Remove items that may collect water such as old tyres and empty pots from around your home to reduce the places where mosquitoes can breed
- Use repellents that are safe for children. Most skin repellents are safe for use on children aged three months and older. Always check the label for instructions
- Use an infant carrier draped with mosquito netting to protect infants aged less than three months, secured along the edges
- While camping, use a tent that has fly screens to prevent mosquitoes entering or sleep under a mosquito net
Information on eligibility for a free JE vaccine is available at Japanese encephalitis vaccination.
Mosquito borne diseases cannot be transmitted directly between humans or from any other animal.
For further information on JE virus and ways to protect yourself visit Mosquito borne diseases.
