It's the first case of the virus detected in the state this season.

The person is a resident of the Campaspe local government area in the state's north and authorities have not released details about their condition.

The area was hit hard by flooding over recent months in towns including Echuca and Rochester, along the Murray River.

Last week a man in his 80s from South Australia's Riverland region was admitted to hospital with the virus and another man from central NSW was diagnosed with the condition.

The virus is spread by mosquitoes and most people will experience no symptoms but about one per cent of cases will become severely unwell.

Symptoms can include confusion, headaches, vomiting, seizures, disorientation and may lead to neurological damage or death.

The Victorian health department said people who spend time working or camping outdoors in inland riverine areas or the Murray River were at increased risk of exposure.

Vaccine supply is limited in Australia but it is free for Victorians in flood-affected areas.

Australian Associated Press