The Department of Primary Industries has quarantined two commercial duck farms operated by the same owner, after birds at both properties tested positive to low pathogenic avian influenza (LPAI).

DPI chief veterinary officer Andrew Cameron yesterday said analytical tests carried out at the Australian Animal Health Laboratory at Geelong had given a positive response to low pathogenic H5 subtype avian influenza virus, prompting authorities to act immediately.

The cases were detected during routine testing for other conditions.

``Avian influenza, also referred to as AI or bird flu, is a contagious disease that affects birds. The transmission of the AI virus from birds to humans is a rare event,'' Dr Cameron said in a statement.

This low pathogenic subtype of avian influenza was not the highly pathogenic H5N1 virus affecting poultry and humans throughout much of Asia, and the wider community was not at risk, he said.

``The virus is relatively harmless now, but we do not want to take the risk it could linger in bird populations and mutate over time to a more virulent strain,'' Dr Cameron said.

He said that arrangements would be made to humanely put down the ducks to prevent further spread.