Highly pathogenic avian influenza (HPAI) subtype H5Nx viruses of the A/Goose/Guangdong/1/1996 (Gs/Gd) lineage have caused substantial economic losses in the poultry industry and represent a significant public health concern. Since its first detection in 1996, it has diverged into 10 genetically distinct hemagglutinin (HA) clades (0–9) and subclades. Of these, the clade 2.3.4.4b HPAI H5N1 viruses have caused outbreaks in wild birds, poultry, and mammals in broad geographical regions including Asia, Europe, Africa, North America, South America, and Antarctica since 2020. In particular, wild aquatic birds have played a key role in the maintenance and global spread of clade 2.3.4.4b HPAI viruses.

In South Korea, the clade 2.3.4.4b HPAI H5N1 viruses caused multiple outbreaks in wild birds, including 67 reported cases from October 2021 to March 2022, and 174 reported cases from October 2022 to March 2023. During October 2022-March 2023, the HPAI H5N1 virus was detected in 22 wild bird species. Particularly, there was a mass die-off event of 221 hooded cranes (Grus monacha) in Suncheon Bay, South Korea during November–December 2022. We conducted whole genome sequencing and comparative phylogenetic analysis of the isolates from hooded cranes. To elucidate the histopathological changes induced by clade 2.3.4.4b H5N1 HPAI viruses in hooded cranes, histopathological evaluation and immunohistochemistry were conducted on a hooded crane (sample no. 22WC-042) found dead in Suncheon Bay during November 2022.