Since its emergence in US dairy cattle, highly pathogenic avian influenza (bird flu, H5N1) has defied control, spreading to other species and disrupting every stage of the dairy sector. A newly published invited review in the Journal of Dairy Science presents the most comprehensive look yet at the virus's impact and calls for a unified response. With current science pointing to complex transmission dynamics and broad consequences, the authors argue that only a One Health approach, taking into account the intersection of animal and human health with that of the environment, can effectively combat H5N1 and prevent future outbreaks.