Regional Victoria has reported the probable first summer case of a potentially fatal virus spread by mosquitoes.

The Department of Health said Tuesday that a person in the northern portion of the state has been found to have Japanese encephalitis, a flavivirus linked to dengue and yellow fever.

Environmental surveillance has also detected the virus in mosquitoes and wild pigs in New South Wales, as well as along the Murray River in northern Victoria.

The disease is transmitted by mosquitoes and 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.

Victoria's Acting Chief Health Office Christian McGrath issued the alert and warned those near the Murray River or adjacent regions to take extra precautions.

These include using repellent on exposed skin and wearing long, loose fitting clothing when outside, and ensuring accommodation, including tents are properly fitted with nets.

'The risk of mosquito-borne diseases remains high in the coming weeks. Taking measures to avoid mosquito bites is critical to protect against infections,' Dr McGrath said.

It comes after a public plea was issued in Queensland last week after wet weather created ideal mosquito breeding conditions, increasing the risk of Japanese encephalitis spreading from NSW.

More than 50 NSW local government areas had been identified at 'higher risk' of the virus, with it also detected in routine mosquito surveillance in the northwest Riverina region.

Risk of infection increases in the warmer months from November to March due to a higher number of mosquitoes.

Children aged under five and older people who are infected with the virus are at a higher risk of developing more severe illness, such as encephalitis

Mosquito testing is being carried out over the summer period to help identify high risk areas.