A long-nosed fur seal has tested positive to H5N1 bird flu in South Australia.
It's the first confirmed case in a mammal since the virus reached the mainland in June.
The seal was found dead by a member of the public earlier this month.
Authorities are working to contain the growing mortality rate of the latest outbreak, including by vaccinating the colonies of little penguins in Victoria after one tested positive for the virus.
Background
H5N1 bird flu arrived in Australia in June 2026, the last continent to be hit by the strain that has caused mass die offs worldwide.
Since then, it's spread to wild birds in every state.
As of 22 August, 298 "events" had been confirmed nationwide.
An event can range from one to hundreds of infected animals at one location.
The seal case follows a spike in mass bird deaths.
More than 1,000 crested terns have died across three separate events in SA, and Tasmania has lost dozens of penguins on King Island.
Victoria is vaccinating more than thousands of little penguins on Phillip Island after a bird from that colony died.
SA is now considering a similar vaccination program, starting with captive animals at Adelaide Zoo and Cleland Wildlife Park.
The vast majority of positive cases have been reported in greater crested terns.
Seals
A fur seal was found dead at Beachport, on SA's south-east coast, on 19 August.
Testing confirmed it was infected with the H5N1 bird flu.
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Officials say the seal showed no signs of injury and its death doesn't appear linked to any other sick or dead marine mammals.
The South Australian Government reported a suspected second seal infection on Monday.
It isn't the first time bird flu has hit Australian seals.
Thousands of baby seals died on Heard Island, a remote Australian territory 1,500km north of Antarctica, after the virus reached there in late 2025.
It is, however, the first case on the mainland.
On Sunday, Agriculture Minister Julie Collins said of the mainland case: "While the development is concerning, it is not unexpected in areas where infection rates are high among wild birds".
Bigger picture
The seal case follows a spike in mass bird deaths.
SA Premier Peter Malinauskas told state parliament last week that more than 1,000 crested terns have died across three mass mortality events on remote islands.
Victoria is vaccinating thousands of little penguins on Phillip Island after a bird from that colony died.
SA is now working on a similar vaccination program, starting with captive animals at the state's zoos and wildlife parks.
What's next?
There have been no detections in poultry or Australia's agriculture industry.
Authorities say chicken and eggs remain safe to eat, and the risk to human health stays low.
No human cases have been recorded in this outbreak.
Most human cases are mild, causing conjunctivitis or flu-like symptoms, but severe illness and death can occur in rare cases.
National Cabinet (all state and territory leaders) will discuss the latest developments and Australia's ongoing response later this week.
