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Japanese encephalitis is a rare but serious illness caused by the Japanese encephalitis virus (JEV). It is spread to humans by infected mosquitoes.
Japanese encephalitis fact sheet
While Culex species of mosquitoes are most likely to be carrying the virus in NSW, mosquitoes are hard to identify and may also carry other viruses such as Ross River, Barmah Forest and, rarely, the virus that causes Murray Valley encephalitis, so it is important to protect yourself against all mosquitos.
Before the 2021-2022 mosquito season, Japanese encephalitis virus had rarely been found in Australia with previous cases noted only in Northern Australia, Cape York and the Torres Strait.
It is not known how Japanese encephalitis virus came into mainland Australia, but the movement of infected mosquitoes or migratory water birds may have played a part in the virus' spread, combined with significant rain events.
Japanese encephalitis virus has now been detected in pigs and humans in Western and Southern NSW, as well as in Queensland, Victoria, the Northern Territory and South Australia.
Animals can be infected with the Japanese encephalitis virus, but they cannot transmit the virus to humans. It cannot be transmitted by touching or eating meat from an infected animal.
Not all mosquitoes in NSW carry the Japanese encephalitis virus, but some do carry JEV as well as other diseases such as Barmah Forest, Ross River and more rarely, the virus that causes Murray Valley encephalitis. The best thing you can do is take steps to prevent being bitten.
NSW recommends people continue to avoid mosquito bites this summer: spray up (use repellent), cover up (wear long-sleeved shirts and long pants), screen up (cover windows and doors with insect screens) and clean up (remove any containers that hold water where mosquitoes may breed). Further information is available at Mosquito-borne diseases.
No human cases were reported in the 2023-2024 season.
