Victorians are being warned of possible cases of Japanese encephalitis in the state, after several animals were treated for the virus in the past month.

There are no confirmed cases of the Japanese strain of the virus in Victorian patients yet.

However, evidence of the strain has been found in pigs in Echuca, in New South Wales near the Victorian border, as well as in southern Queensland.

Chief Health Officer Brett Sutton said the disease can be very serious and even life threatening.

"Most people with Japanese encephalitis will have no or very mild symptoms, but anyone who develops a sudden onset of fever, headache and vomiting should see their doctor immediately," he said in an update issued on Sunday.

"People with these symptoms can deteriorate over just a few short days, including suffering a loss of co-ordination, disorientation, generalised weakness and in some cases issues with movement which can last for years."

The virus is spread through mosquito bites and people in regional areas who are in contact with pigs may be at particular risk.

Anyone working or camping in country Victoria is being warned to use mosquito repellent and cover up with loose-fitting clothing.

Older people and those aged under five who are infected are at higher risk of developing serious illness.