“At this stage it is not a confirmed detection … seeing signs consistent with H5 bird flu in wildlife on Heard Island is not unexpected,” the Agriculture Department said in a statement.

H5 bird flu has spread widely in wild birds worldwide and is causing outbreaks in poultry and US dairy cows, with several recent human cases in US dairy and poultry workers.

Australia remains the only continent free of the highly contagious viral flu, somewhat protected by its geography as it is off the migration routes of big birds such as geese that spread infection. The virus has reached neighbouring Indonesia in 2022 and Antarctica in 2023.

Some other strains of bird flu were reported in poultry farms in Australia last year but none were the H5N1 variant.

Australian officials said its Antarctic programme scientists on a visit to Heard Island, more than 4,000km southwest of Perth and 1,700km north of Antarctica, found more deaths among elephant seals than penguins and other seabirds.

But authorities said a confirmed case of bird flu there would not substantially increase the risk to Australia.

The H5 virus has previously been found on the French Kerguelen and Crozet sub-Antarctic islands, which are less than 450km from Heard and McDonald Islands.

Samples collected will be tested once the scientists return to Australia in the middle of November.