The virus was discovered during an expedition in October 2025, when researchers traveling to the islands noticed the islands were covered in dead seals.
Genetic tests confirmed that the H5 virus had also killed penguins and other birds. Southern elephant seal pups were hardest hit, with mortality rates in some colonies reaching 97 percent.
Scientists believe the infection came in August 2025 via animals from the Crozet Islands. It is the first time the virus has been detected in an Australian external territory and is seen as another sign that the infection is spreading eastward. The archipelago is located 4,000 kilometers southwest of Australia and is uninhabited.
