A potentially deadly mosquito-borne virus has been detected in north-western Victoria, prompting a warning from health authorities.

The Victorian Health Department confirmed the first detection of Japanese encephalitis virus in mosquitoes for the 2025–26 season in a mosquito trap in the Horsham Rural City Council area.

Japanese encephalitis (sometimes called JEV), a flavivirus related to dengue and yellow fever, is transmitted by mosquitoes and can cause serious infection of the brain.

Most people do not become sick but symptoms can include a fever, vomiting and headaches.

In more severe cases patients can experience seizures, paralysis, permanent disability or even death.

Last summer there were a handful of cases in Victoria, with most people believed to be exposed to the disease near the Murray River in the NSW Riverina region.

In March, an ACT man died from JEV after contracting the disease while holidaying in the Murrumbidgee region. He was the second to die from the virus in NSW last summer.

In the 2024-25 summer, the virus was detected along the Murray River from Mildura in Victoria’s north-west to Moira in, and in piggeries across all three eastern states.

Human cases of Japanese encephalitis were also reported in Queensland, including for the first time in Brisbane.

“Mosquito-borne diseases like Japanese encephalitis can have serious health impacts, but they are preventable,” Victoria’s Chief Health Officer, Dr Caroline McElnay, said on Tuesday.

“A free Japanese encephalitis vaccine is available for eligible people due to their increased risk of exposure.

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

“Anyone can be bitten by mosquitoes, but people living, working or spending time outdoors in northern Victoria – especially near rivers – may be at higher risk.”

A free Japanese encephalitis vaccine is available in 24 local government areas across Victoria, including Horsham Rural City Council, for eligible people at increased risk.

Free JEV vaccines are also available in some NSW local government areas. More details are available from NSW Health.

Vaccines can be given even for those not eligible for Medicare. A booster dose a year or two later may be recommended for some people with ongoing risk of exposure.

More information is available from the Department of Health or the Better Health Channel websites.