Abstract Title
The changing face of clade 2.3.4.4b H5N1 - a focus to Europe
Abstract
Since 2020, the European poultry industry has suffered from four consecutive large epidemic waves caused by the highly pathogenic avian influenza H5 viruses of clade 2.3.4.4b. During these epidemics, we witnessed unprecedented changes in the ecology, epidemiology and evolution of the virus, which began to endemically circulate in wild birds in Europe infecting a progressively wider number of hosts, with devastating consequences for the poultry industry in several European countries. With about 90 different genotypes identified at different frequency levels, this virus has demonstrated a high propensity for reassortment. A rapid turnover among genotypes was observed, with few of them showing a persistent circulation throughout multiple waves. We demonstrated that different genotypes may occupy separate ecological niches and have different spatial and temporal spread patterns, leading to varying risk scenarios for both wild and domestic animals. Among the hosts, Anseriformes - and consequently genotypes mainly circulating in this host order – turned out to be the most important infection source for poultry. In turn, on several occasions poultry in Europe was recognized as having directly or indirectly acted as a virus source for domestic and companion mammals, i.e. cats and ferrets. Alarmingly, some spillback transmissions have involved viruses with mammalian-adapted mutations, reintroducing these back into poultry — an ideal setting for virus amplification. In this scenario, increasing surveillance and sequencing efforts are crucial to spot possibly unseen chains of transmissions at the bird-mammalian interface, which may represent an important threat for the emergence of strains with increased pandemic potential.
Co-Author(s)
Alice Fusaro
European Reference Laboratory (EURL) for Avian Influenza and Newcastle Disease, Istituto Zooprofilattico Sperimentale delle Venezie, Legnaro (PD), Italy
Abstract Category
Notable outbreaks, field and molecular epidemiology, and surveillance in poultry