Key facts
- H5N1 bird flu confirmed on Macquarie Island.
- Virus found in elephant seals and kelp gulls.
- Pup mortality rates can exceed 90% in seals.
- Personnel withdrawn from research station due to outbreak risk.
Australia confirmed its first case of H5N1 bird flu on the sub-Antarctic Macquarie Island on Saturday, October 17. The highly pathogenic virus strain was detected in samples collected from an elephant seal and a kelp gull. This marks the first H5 event on the island, which is a key breeding ground for southern elephant seals. In late 2025, over 13,000 baby seals were killed by the virus on another Australian sub-Antarctic territory, Heard Island. Mammals like the southern elephant seal, which can weigh up to 3,600 kg, are highly susceptible to H5 bird flu, with pup mortality rates potentially exceeding 90%. In August, Australia's environment department withdrew personnel from a research station on Macquarie Island due to the risk of an outbreak, with experts predicting a significant mortality event during the upcoming breeding season.