The gentoo penguin has become the first bird to test positive for the H5N1 bird flu on an Australian territory, with samples confirming the virus has spread on a sub-Antarctic island.

The deadly and contagious strain of bird flu, which has already killed millions of seabirds, wild birds and poultry overseas, was confirmed in southern elephant seals on Heard Island in November 2025.

Fur seals and gentoo penguins have now tested positive for the virus, according to the federal government, after further samples were collected by Australian Antarctic Program scientists on a second voyage to Heard Island.

The island is an Australian territory located about 4,000km south-west of Perth, and 1,700km north of Antarctica.

Prof Hugh Possingham, the vice-president of BirdLife Australia, said the spread of the virus to other species was “a very concerning development”.

“The gentoo penguins of Heard Island are now the first birds in an Australian territory to test positive for this virus that has devastated wildlife around the world,” Possingham said. “They will certainly not be the last.”

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He said H5N1 could pose a significant threat to the survival of other Australian birds, including the Heard Island cormorant and Heard Island sheathbill, which are species found nowhere else on Earth.

“Since the virus was first suspected and subsequently confirmed on Heard Island, we’ve been asking the government very directly how protections for wildlife are being ramped up to safeguard Australian wildlife from this virus that is very clearly on the move,” he said.

“We’re disappointed that those questions largely remain unanswered.”

In an update on Tuesday, the federal government said Australia remained free of H5N1, and the additional detections did not substantially increase the risk.

The agriculture minister, Julie Collins, said the government took the threat of bird flu seriously, and had invested more than $100m to strengthen preparedness and response capability.

“While continued detections of H5 bird flu on Heard Island are not unexpected, this does reinforce the ongoing need for Australia to remain focused on preparing for a potential outbreak,” she said.

“Biosecurity is a shared responsibility, and Australia’s success depends on close cooperation between governments, industry, communities and individuals.”

The H5N1 virus entered the Antarctic in the 2023-24 season, with the first detections in South Georgia and then the Antarctic peninsula. In the next year, it spread to Marion Island and the French Kerguelen and Crozet sub-Antarctic islands, located about 500km from Heard and McDonald islands.

Dr Michelle Wille, an expert in avian influenza viruses at the University of Melbourne, described the disease as “catastrophic for wildlife” and said H5N1 had already spread thousands of kilometres over the ocean.

She said it was “conceivable that the virus could theoretically spread from where it is now, into Australian [and] New Zealand sub-Antarctic islands like Macquarie Island. And from there it’s not very far to get to Australia itself.

“We are at risk of this virus arriving to Australia, either from this potential southern route, or from a northern route,” she said, which made surveillance and preparedness extremely important.