A supermarket giant has slapped limits on egg purchases due to a growing bird flu outbreak, as farmers focus on efforts to maintain supplies.

The highly pathogenic H7N3 strain of bird flu has been detected on five farms in Victoria’s  south-west, with more than half a million chickens so far euthanised in an effort to stop the spread of the disease.

Coles customers in every state and territory can buy a maximum of two egg cartons, with the exception of Western Australia.

Coles said the limit was temporary but had not revealed how long it was expected to last.

“We are working closely with all of our suppliers to ensure eggs remain available for our customers and we are providing support to the industry in responding to the avian flu cases in Victoria,” a Coles spokesperson said.

Rivals Woolworths and Aldi and other national retailers have not followed Coles with any similar purchase limits.

The virus has been detected on five farms linked to Farm Pride, Avgo, Surf Coast Eggs and another business in recent weeks. The affected farms in Meredith, Lethbridge and Terang have been locked down, with at least 580,000 birds euthanised.

Federal Health Minister Mark Butler said the chief medical officer has been regularly briefing him on the outbreak and stressed it was a different variant to forms of the disease overseas that have crossed over into humans.

“I know [Australians] will want to know that they’re going to have access to enough eggs to keep having the hearty Australian breakfast, so we are taking this seriously,” Butler told ABC TV.

“This is a significant issue globally, the avian flu that it is sweeping the globe.

“I’m making sure that our government particularly is across any implications that might have for human health, at the moment we feel very confident about that but I know the agricultural industry is worried about this as well.”

Victorian Farmers Federation vice-president and egg farmer Danyel Cucinotta said the industry was ramping up containment efforts to ensure eggs remained available. She advised customers to shop around at local retailers.

“Victorian egg farmers are working hard to contain the risk of any further biosecurity outbreak and maintain a supply of fresh and affordable eggs,” Cucinotta said.

Victoria’s chief veterinary officer Graeme Cooke has said eggs and poultry products from retailers did not pose a health risk and were safe to consume.

Avian influenza is a viral disease found across the globe that spreads between birds or when feed and equipment is moved between sites.

The US has imposed restrictions on imports of Victorian eggs and poultry products.

– AAP