More than 13,000 elephant seal pups died on a remote Australian island after a highly contagious bird flu strain swept through their breeding colony. Scientists from the Australian Antarctic Program confirmed the H5 virus killed seals, penguins and birds on the Heard and McDonald Islands, a sub-Antarctic territory located 4,000 kilometers southwest of mainland Australia.
A breeding ground turned into a graveyard
Researchers arrived on a research expedition in October 2025 and found the rocky outcrop littered with seal carcasses. Ground and aerial surveys conducted in October 2025 and January 2026 counted 13,300 dead elephant seal pups. In some seal groups called harems, mortality reached as high as 97 percent. Genetic testing confirmed the H5 bird flu strain had been detected for the first time in one of Australia's external territories.
How the virus arrived on an uninhabited island
Biologist Julie McInnes said the observations marked the first detection of H5 bird flu in an Australian external territory and showed the continued eastward movement of the virus. Scientists believe infected wildlife carried the virus from the Crozet Islands, a sub-Antarctic archipelago about 1,500 kilometers to the northwest, likely arriving in August 2025. The Heard and McDonald Islands are uninhabited by humans and access is allowed only with permission from the Australian government.
A place that recently made global headlines for a different reason
The islands unexpectedly hit international news in April 2025 when former US President Donald Trump included them on a list of international tariffs. Now they are in the spotlight again for a far more devastating reason. The islands are fearsomely wild, and the scale of the die off has shocked scientists who study the region's fragile ecosystem.
The outbreak shows how bird flu continues to spread into some of the most isolated places on Earth. The virus has now reached a remote Australian territory, killing thousands of young seals and raising questions about how wildlife diseases move across vast ocean distances.
