Beware of Japanese Encephalitis Virus During Australian Summer Vacation

The first detection of Japanese encephalitis virus (JEV) for the 2025-2026 summer season has been confirmed in a mosquito near Horsham Rural City Council, Victoria. 

While rare, the Australian Centre for Disease Control (ACDC) says JEV spreads through bites from infected mosquitoes and can cause severe brain inflammation (encephalitis). It is fatal in about 1 in 250 patients.

Victoria's Chief Health Officer, Dr Caroline McElnay, said in a press release, "Mosquitoes can bite anyone, but people living, working or spending time outdoors in northern Victoria – especially near rivers – may be at higher risk."

"Simple actions like wearing repellent, covering up, and limiting outdoor activities at dawn and dusk can help reduce your risk."

JEV is the leading cause of viral encephalitis in 24 countries in the Pacific/Oceania Regions, exposing more than 3 billion people to infection risks.

As of December 24, 2025, nine JEV cases and five deaths were reported in Australia during the 2024–25 summer, with many more cases likely going unreported because, in most instances, people don't have any symptoms.

In 2022, JEV was detected in south-eastern Australia for the first time, with 45 human cases and seven deaths reported.

The ACDC has written that an effective preventive vaccine for JEV is available for people at higher risk of contracting the virus in Australia. If you are not eligible for a free JEV vaccine but are at higher risk, you can talk to your healthcare professional about buying one privately.

When departing from the United States, JEV vaccines are commercially offered at travel vaccine clinics.

Furthermore, the risk of JE introduction into the U.S. may be highest in California due to the frequency of international arrivals from Asia and Australia and the abundance of mosquitoes.