Australia confirms first H5N1 case on sub-Antarctic Macquarie Island

Australia has confirmed its first case of H5N1 bird flu on the sub-Antarctic Macquarie Island, with the deadly virus detected in the remote territory’s vulnerable elephant seal population. (Reuters)

Chief Veterinary Officer Beth Cookson said official testing had confirmed the highly pathogenic strain “in samples collected from an elephant seal and a kelp gull on Macquarie Island, marking the first H5 event on this island”. (Reuters)

Macquarie Island, a UNESCO World Heritage-listed Australian territory in the Southern Ocean halfway between Tasmania and Antarctica, is a key breeding ground for southern elephant seals. (Reuters)

The seals, which can weigh up to 3,600 kg (7,936 lb), are particularly susceptible to H5 bird flu, with pup mortality rates exceeding 90% in some outbreaks, according to the federal government. (Reuters)

In August, Australia’s environment department said it would withdraw personnel from the island’s research station over the “psycho-social risk to expeditioners of a potential H5 avian influenza outbreak”. (Reuters) Expert assessments predicted the virus would likely cause a significant elephant seal mortality event during the upcoming breeding season, the department said. (Reuters)

The confirmation comes after Australia in June became the last continent to report bird flu. The virus was detected in late 2025 on Heard Island, another sub-Antarctic Australian territory, where local media reported it killed more than 13,000 baby seals. (Reuters)