Houses isolated as Victorian floodwaters rise

600 properties face isolation in Victoria. Photo / Getty Images

About 600 properties face isolation as floodwaters continue to rise in northern Victoria.

Premier John Brumby said hundreds of properties in Shepparton and Kialla could be cut off by floodwaters.

He said 40 businesses were sandbagged for protection on Tuesday night.

"The river there has not yet peaked. It's been a bit slower coming through than the authorities thought," he told reporters in Seymour, south of Shepparton.

"We have got a number of farm areas that are isolated and could be isolated for some days.

"The briefing I got ... is that those waters will subside pretty rapidly once the peak is reached."

About 20 properties are thought to be flooded in Horsham, in the state's west, where the river has not yet peaked.

The levee bank in Wangaratta, in the state's north, continues to hold.

Mr Brumby warned people living in flood-affected areas to be mindful of sanitation, as the health department has warned of an outbreak of Ross River fever as floodwater recede.

"If you are in any area where there has been significant flooding, you should be boiling your water as a precaution," he said.

"The basic things after all of these emergencies are washing hands after contact.

"There is a lot of muck that gets washed down rivers; there is a lot of sewerage systems that overflow and so personal hygiene is really important.

"Then of course you've got mosquito issues. Again (it's about) making sure that people are conscious of that, using the Aeroguard, using the protections and guarding against any mosquito-borne illnesses."

The premier said moderate flooding across the state was likely during the next few weeks.

"The ground is so wet and so sodden that any rain that falls will tend to run quickly and add to any flood impacts," he said.

"We need to get busy cleaning up, but we also need to recognise there is going to be a continuing flood threat.

"The clean-up is going to take weeks and weeks."

Seymour residents were door-knocked by State Emergency Service volunteers on Tuesday night advising them of the flood risk, but damage to the area so far is minimal.

- AAP