On the southern coast of Australia, a long-nosed fur seal has become the first mammal on the continent confirmed to carry the H5 bird flu virus — a quiet but significant crossing of a biological threshold. The infection, traced to contact with wild birds near Beachport in South Australia, arrives within an outbreak that has already touched 298 recorded events, with the state itself bearing the heaviest burden. Authorities are watchful but measured, noting no spread to other marine mammals and no breach of the agricultural systems that feed the nation. In the long story of viruses and the bound