The role of wild birds in the global highly pathogenic avian influenza H5 panzootic, 2020–2023

The emergence of Highly Pathogenic Avian Influenza (HPAI) H5 clade 2.3.4.4b has triggered an unprecedented global panzootic in recent years. As the frequency and scale of HPAI H5 outbreaks continue to rise, understanding how wild birds contribute to shape the global virus spread across regions-affecting poultry, domestic and wild mammals-is increasingly critical. In this review, we examine ecological and evolutionary studies to map the global transmission routes of HPAI H5 viruses, identify key wild bird species involved in viral dissemination, and explore infection patterns, including mortality and survival. We also highlight major remaining knowledge gaps that hinder a full understanding of wild birds' role in viral dynamics, which must be addressed to enhance surveillance strategies and refine risk assessment models aimed at better predicting future outbreaks in wildlife and mitigating outbreaks in domestic animals to safeguard public health.