Since October 30, 2020, there have been over 30 recorded outbreaks of high pathogenicity avian influenza (HPAI) in domestic poultry and wild fowl in Japan. This outbreak was caused by the influenza A virus H5N8, a known High Pathogenicity Avian Influenza Virus (HPAIV). In such a scenario, identification of the source of the virus and its transmission route is important to control its spread.