The article provides a comprehensive overview of the highly pathogenic avian influenza (HPAI) virus H5N1, its ecology, transmission to humans, and the potential pandemic threat it poses. H5N1 viruses are highly contagious among poultry and have caused significant economic and social impacts in developing countries. While the virus can infect humans, its transmission from birds to humans remains inefficient, and human-to-human transmission has not yet occurred. The article discusses the biological properties of influenza viruses, including their genetic makeup and receptor specificity, which influence interspecies transmission. It highlights the role of live-poultry markets and backyard poultry in maintaining and spreading the virus within and between regions. The emergence and spread of H5N1 viruses in Asia, particularly in wild bird populations, are described, along with the challenges in controlling its transmission. The clinical spectrum of human H5N1 infections, including symptoms, complications, and mortality rates, is detailed. The article also addresses diagnostic methods, antiviral treatments, and intervention strategies to control the spread of H5N1. Finally, it concludes by emphasizing the need for continued surveillance and research to better understand and manage the threat posed by H5N1.The article provides a comprehensive overview of the highly pathogenic avian influenza (HPAI) virus H5N1, its ecology, transmission to humans, and the potential pandemic threat it poses. H5N1 viruses are highly contagious among poultry and have caused significant economic and social impacts in developing countries. While the virus can infect humans, its transmission from birds to humans remains inefficient, and human-to-human transmission has not yet occurred. The article discusses the biological properties of influenza viruses, including their genetic makeup and receptor specificity, which influence interspecies transmission. It highlights the role of live-poultry markets and backyard poultry in maintaining and spreading the virus within and between regions. The emergence and spread of H5N1 viruses in Asia, particularly in wild bird populations, are described, along with the challenges in controlling its transmission. The clinical spectrum of human H5N1 infections, including symptoms, complications, and mortality rates, is detailed. The article also addresses diagnostic methods, antiviral treatments, and intervention strategies to control the spread of H5N1. Finally, it concludes by emphasizing the need for continued surveillance and research to better understand and manage the threat posed by H5N1.