Australia confirms first H5N1 bird flu case in mammals after seal dies due to infection

Australia’s hard-fought defense against avian influenza has suffered a major setback.

Authorities have confirmed the country’s first mainland case of H5N1 bird flu in a mammal, after a long-nosed fur seal washed ashore in South Australia, escalating an outbreak that has already swept through hundreds of wild birds.

The country has been grappling with rising cases of the highly pathogenic avian influenza after it landed in the country in June.

The seal was found dead on August 19 by a member of the public in the coastal town of Beachport, South Australia about 300 km south of Adelaide.

The virus first reached Australia's mainland via migratory seabirds and has since resulted in nearly 300 confirmed H5 bird flu events across wild bird populations.

While remote sub-Antarctic territories like Heard Island experienced mass seal mortalities previously, this marks the first official detection in a mainland marine mammal.

H5N1 has not shown up in Australia’s poultry or agriculture, according to the federal government, which said on Friday that 297 cases have been confirmed nationwide.

Federal Agriculture Minister Julie Collins noted that while the detection in wildlife is concerning, commercial poultry and agricultural systems remain unaffected with zero confirmed cases in farms.

Australia was the last continent to report bird flu, although the virus was detected in late 2025 on the sub-Antarctic territory of Heard Island.

As reported more than 13,000 baby seals were killed by the virus on the island, according to local media.

South Australia's chief veterinary officer, Skye Fruean said, seals are at high risk of contracting the virus 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," said Fruean.