Speaker
Description
Genetic reassortment, the exchange of gene segments between distinct influenza A virus genomes, is a key mechanism driving the emergence of novel variants. In avian influenza viruses, reassortment are extremely frequent and accompanies phenotypic changes. Since 2020, clade 2.3.4.4b H5 high pathogenicity avian influenza viruses (HPAIVs) have driven a global panzootic, causing mass mortality in wild birds, poultry and repeated spillover infections in a variety of mammalian species. This resurgence of H5 HPAIV has coincided with a dramatic increase in the number of circulating reassortant strains; however, the scale, impact and drivers of these reassortants remain unknown. Here, we combined statistical and phylodynamic modelling to reconstruct the global evolutionary dynamics of H5Nx viruses across four epizootic seasons. We identified over 200 genetically distinct reassortants, stratified into three transmission categories based on their phylogenetic and epidemiological profiles. Statistical modelling revealed that reassortant success was strongly shaped by ecological factors, including circulation in specific wild bird orders and the ability to infect a wider range of host niches. Collectively, our findings reveal reassortment dynamics in H5 HPAIVs and identify key virological and ecological. These insights support the importance of enhanced surveillance to track evolution of H5 HPAIV and identify traits relevant for consideration in pandemic risk assessment.
