Avian influenza in the context of a pandemic challenge.

Highly pathogenic avian influenza viruses (HPAIVs) have undergone ecological and evolutionary shifts in recent years, broadening both their host range and geographic distribution. This manuscript explores the emergence and dissemination of HPAIVs, tracing their origins from wild waterfowl reservoirs to domestic poultry, and examining their increasing ability to infect mammalian species, including swine and humans. We detail the molecular transition insights from low pathogenic avian influenza to highly pathogenic avian influenza (HPAI) within poultry populations as drivers of adaptation and enhanced virulence. Key zoonotic episodes involving human and other hosts are reviewed, with attention to the role of viral reassortment and adaptation. Current risk assessments are analyzed, suggesting measures to mitigate the impact of HPAI from a One Health perspective, including public health interventions, coordinated international surveillance, early warning and containment systems, as well as prophylactic and therapeutic options.