The remote Australian territory of Heard Island in the subantarctic has been ravaged by a devastating outbreak of H5N1 avian influenza, resulting in the deaths of over 13,000 southern elephant seal pups. This catastrophic event, observed between October 2025 and January 2026 by government scientists, highlights the alarming spread of this highly pathogenic virus across the sub-Antarctic region.
The H5N1 strain has now been confirmed in six out of nine species on Heard Island, including southern elephant seals, Antarctic fur seals, king penguins, gentoo penguins, and South Georgia diving petrels. The usually low pup mortality rate of below 5% annually skyrocketed to an average of 76%, with a staggering 97% recorded in one specific location.
Genetic analysis suggests that the virus originated from the French subantarctic Crozet Islands approximately 1,800 kilometres away, likely arriving on Heard Island in August of the previous year. This marks the first detection of H5 bird flu in an Australian external territory and underscores the virus's relentless eastward spread across the sub-Antarctic region.
The Australian Antarctic Program is actively monitoring for further signs of bird flu in the Australian Antarctic Territory and on Macquarie Island, where no suspected cases have yet been reported. In response to this escalating threat, the federal government has allocated an additional A$11.2 million in its 2026-27 budget to prepare for potential impacts on native species across the mainland.
Australia's Environment Minister, Murray Watt, acknowledged the current absence of H5 bird flu on the mainland but cautioned against complacency, citing the virus's global spread and the possibility of a southern incursion. Dr Michelle Wille, an expert in avian influenza viruses at the University of Melbourne, described the survey results as "devastating" and consistent with outbreaks observed elsewhere in the subantarctic.