Australia has recorded its first mass mortality event as H5N1 bird flu continues to spread across the country.

Agriculture Julie Collins made the announcement on Monday, saying there were now 74 confirmed cases of the H5 strain.

Of those, 10 were in Western Australia, 54 in South Australia, two in New South Wales, seven in Victoria, and one in Queensland.

“I can also say that CSIRO laboratory testing has now confirmed that the H5 bird flu samples that were taken from a larger group of sick and dead birds at Borden Rocks off Cape Jaffa in South Australia have come back positive,” Ms Collins said.

“Whilst this is the first confirmed case of a mass mortality, and obviously a very concerning development, it is not unexpected, and is certainly what we have seen overseas with this type of incursion of the H5.”

She said ongoing surveillance would help officials determine if H5 spreads more broadly.

“Australians should expect to see more spread and larger numbers now of wildlife being affected,” Ms Collins said.

There has been no detection of any H5N1 in the poultry industry.

Environment Minister Murray Watt said the mass mortality event was “very sad news”.

“This is the beginning of what is likely to be a long, difficult journey, in terms of the impacts on wildlife,” he said.

“The overseas experience has shown that we can’t stop the spread of H5 bird flu among birds or among mammals... and that will mean more mass mortality events.”

He said an additional $24 million was released last week across the states, territories, and Commonwealth, in addition to the $113 million already invested from the Albanese government.

The first detection in Australia was June 20.

Mr Watt said every bird species was at risk, with Chief Veterinary officer Beth Cookson adding that numbers would likely increase during migratory bird season.

“It’s like clockwork every year for some of those species and where they congregate in numbers, mixed with other bird species in Australia which may already be infected, there is absolutely increased risk of transmission, and further mortality events,” Dr Cookson said.

Ms Collins said greater crested terns and silver gulls had been infected but the list of vulnerable birds was likely to grow.

People with backyard chickens have been encouraged to minimise contact between their birds and wild birds, where possible.

Dr Cookson suggested introducing a quarantine period for hen owners introducing new birds to their flock.

“Stopping that mingling, including contamination potentially of food and water sources and also making sure that there’s good hygiene when handling birds, washing hands in between the like,” Dr Cookson said.