Breaking: Bird flu suspected as over 1,000 birds dead in three mass mortality events

Australia has confirmed its first case of H5N1 bird flu in a mammal, a long-nosed fur seal found dead in South Australia, as authorities grapple with a rapidly evolving outbreak that has now caused mass deaths in seabirds and raised fears for endangered species.

The seal, found at Beachport, about 310 km south of Adelaide, was confirmed positive for the virus by the CSIRO’s Australian Centre for Disease Preparedness (ACDP). Federal Agriculture Minister Julie Collins said the detection, announced on Saturday, was "sadly our first confirmed case of H5 bird flu in a mammal in Australia."

Collins, speaking to reporters in Hobart, described the development as concerning but not unexpected, noting that infection in other wildlife was likely in areas with high infection rates in wild birds. The minister said the seal's death did not appear to be associated with other sick or dead marine mammals, and that the infection likely occurred due to exposure to infected wild birds or the environment they share.

The seal was one of an estimated 100,000 in the state's waters. South Australia's chief veterinary officer, Skye Fruean, said seals are at high risk because they live very near wild birds on rocky outcrops on the coast. "They would be coming across, no doubt, really high levels of the virus in their environment," Fruean said.

Mass mortality events

The mammal case comes days after South Australian authorities identified three mass mortality events involving more than 1,000 dead crested terns, which are presumed to have died from H5N1 bird flu. Premier Peter Malinauskas told SA Parliament the deaths occurred on remote offshore islands, including Troubridge Island off Yorke Peninsula and the North and South Page islands off Kangaroo Island.

The deaths were detected on Wednesday by state government surveillance teams. Malinauskas called the discoveries a "significant escalation" of bird flu in the state. "The loss of more than 1,000 birds is deeply concerning, and the state government is treating these events with the utmost seriousness," he said.

Malinauskas also noted that no mass mortality had been reported in mammals, and that H5N1 had not been detected in poultry or livestock. South Australia has recorded 177 confirmed H5 bird flu cases, the most of any state.

A separate mortality event has been reported in Tasmania, where 28 dead penguins and three dead crested terns were found on the coast of King Island. The birds are being tested for H5 bird flu, which has already killed seven birds on the Bass Strait island.

Spread to seals and penguins

Australia's first confirmed mammal case was followed by a suspected case in another long-nosed fur seal at The Pages Conservation Park, a key breeding ground for the endangered Australian sea lion. The suspected case, yet to be confirmed, was announced by South Australia's Department of Primary Industries and Regions (PIRSA). The Pages islands are also the site of a mass mortality event in birds.

The Invasive Species Council warned that the Australian sea lion could face an "extinction level" event if the disease enters its colonies. Federal Environment Minister Murray Watt said the development was "obviously a very serious development" but not unexpected, adding that more mass mortalities were likely.

A little penguin at Kangaroo Island has also tested positive for H5 bird flu, and a suspected case involving another little penguin is under investigation. In a separate development, a confirmed death of a little penguin on Phillip Island last week was reported.

Government response and vaccination plans

Federal Agriculture Minister Julie Collins stressed that there is no evidence of infection in Australia's poultry or agriculture systems. She said she would travel to South Australia in the coming days to discuss the state's response. Australia has had 298 recorded positive H5 bird flu events, according to 7NEWS, while other reports cite 297 confirmed cases nationwide as of Friday.

Premier Malinauskas said the state was seeking approval for a vaccination programme for penguins and potentially other species, including the black-bellied parrot. The vaccinations, which require two separate injections, would initially be focused on captive animals, such as those at Adelaide Zoo and Cleland Wildlife Park, but no timeline has been set.

A programme to vaccinate more than 5,000 little penguins across Phillip Island and St Kilda began on Monday, according to 7NEWS.

Broader context

Australia was the last continent to report bird flu, though the virus was detected in late 2025 on the sub-Antarctic territory of Heard Island, where more than 13,000 baby seals were killed, according to local media. The virus arrived on the Australian mainland in June, and this month saw the first mass seabird deaths from the virus.

Georgie Cornish, SA primary industries department biosecurity chief, said bird flu reporting had moved from individual cases to events to help people understand how the virus is moving across the landscape. NSW authorities also reported two H5 events involving seven birds on Thursday.

Tasmanian Premier Jeremy Rockliff posted on social media about testing and surging teams, while Wes Ford, Natural Resources and Environment Tasmania incident controller, said there was no evidence of mass mortality in the state and that poultry was safe. The Invasive Species Council's Jack Gough called for urgent investment to protect wildlife from other threats.