Integrated HPAIV surveillance at a crane wintering site in the Izumi Plain

The Izumi Plain, Japan, is a major wintering site for endangered cranes adjacent to intensive poultry production, creating an important interface for avian influenza virus (AIV) surveillance. This Review synthesizes more than a decade of environmental and wild-bird surveillance, focusing on water collected from artificial crane roosts. Initially, virus isolation from roost water was inefficient, yielding few isolates. A modified procedure introduced in the 2018/19 season markedly improved isolation efficiency, yielding 44 low pathogenicity avian influenza viruses (LPAIVs) that season. The increased availability of infectious isolates enabled whole-genome analyses that revealed subtype diversity, reassortment, and genotype turnover, transforming roost-water surveillance from sporadic detection into a tool for characterizing AIV circulation. During the 2022/23 high pathogenicity avian influenza (HPAI) outbreak, extensive crane mortality contrasted with limited HPAIV isolation from roost water, highlighting the limitations of environmental surveillance alone. Integrating environmental, host-based, serological, and genomic data provides a more comprehensive understanding of HPAIV dynamics and strengthens surveillance at high-density wild-bird aggregation sites.