H5N1 Bird Flu Reaches Australian Territory on Sub-Antarctic Island

H5N1 clade 2.3.4.4b has been confirmed across multiple wildlife species on Heard Island, a remote UNESCO World Heritage site 4,000 kilometres southwest of Perth. Australian Antarctic Program scientists finalized the assessment on 18 June 2026, following initial discoveries of dead seal pups in late 2025 and additional wildlife samples in early 2026. The detections occur on uninhabited Australian territory with no mainland incursion. Migratory seabirds with routes to Australian coasts now represent the key surveillance focus for biosecurity planners.