Health authorities in Australia are urging residents and visitors to take precautions against Japanese encephalitis virus ahead of the 2025–26 summer season, after routine surveillance detected the virus in mosquitoes in regional Victoria.

Japanese encephalitis virus, transmitted by infected mosquito bites, can cause serious inflammation of the brain in a small proportion of cases and has been present in parts of Australia since its emergence on the mainland in 2022. The first confirmed detection of the virus this season occurred in a mosquito trap in the Horsham region of western Victoria, prompting public health warnings about mosquito bite prevention and vaccination for those at higher risk of exposure.

Public health officials highlighted that most people infected with the virus experience no symptoms or only mild illness, but a minority can develop severe neurological disease that may be life-threatening.

In recent years, organised surveillance has identified human cases across multiple states, with past seasons seeing several deaths and infections in New South Wales and Queensland, and the virus detected in local mosquito populations and animal hosts.

Health authorities recommend that people living in or travelling to areas with known Japanese encephalitis virus activity consider protective measures including wearing long, loose-fitting clothing, using insect repellent, avoiding outdoor exposure at dawn and dusk when mosquitoes are most active, and reducing stagnant water around homes to limit mosquito breeding.

A safe and effective vaccine is available in Australia for people at higher risk due to their occupation or travel plans, and officials are encouraging eligible individuals to seek vaccination ahead of peak mosquito activity.

Public health agencies continue to monitor mosquito and vertebrate hosts closely and to provide updated guidance to help reduce the risk of infection during the summer holiday period.