Since 2016, A(H5Nx) high pathogenic avian influenza (HPAI) virus of clade 2.3.4.4b has become one of the most serious global threats not only to wild and domestic birds, but also to public health. In recent years, important changes in the ecology, epidemiology and evolution of this virus have been reported, with an unprecedented global diffusion and variety of affected birds and mammalian species. After the two consecutive and devastating epidemic waves in Europe in 2020-2021 and 2021-2022, with the second one recognized as one of the largest epidemics recorded so far, this clade has begun to circulate endemically in European wild bird populations. This study used the complete genomes of 1,956 European HPAI A(H5Nx) viruses to investigate the virus evolution during this varying epidemiological outline. We investigated the spatiotemporal patterns of A(H5Nx) virus diffusion to/from and within Europe during the 2020-2021 and 2021-2022 epidemic waves, providing evidence of ongoing changes in transmission dynamics and disease epidemiology. We demonstrated the high genetic diversity of the circulating viruses, which have undergone frequent reassortment events, providing for the first time a complete overview and a proposed nomenclature of the multiple genotypes circulating in Europe in 2020-2022. We described the emergence of a new genotype with gull adapted genes, which offered the virus the opportunity to occupy new ecological niches, driving the disease endemicity in the European wild bird population. The high propensity of the virus for reassortment, its jumps to a progressively wider number of host species, including mammals, and the rapid acquisition of adaptive mutations make the trend of virus evolution and spread difficult to predict in this unfailing evolving scenario.

中文翻译：

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欧洲2.3.4.4b分支的高致病性禽流感A(H5)病毒——为什么病毒进化趋势更难预测

自2016年以来，分支2.3.4.4b的A(H5Nx)高致病性禽流感(HPAI)病毒已成为全球最严重的威胁之一，不仅对野生和家禽，而且对公众健康也构成最严重的威胁。近年来，据报道该病毒的生态学、流行病学和进化发生了重要变化，受影响的鸟类和哺乳动物物种在全球范围内出现了前所未有的扩散和多样性。在2020-2021年和2021-2022年欧洲连续发生两波毁灭性的流行病之后，第二波被认为是迄今为止有记录的最大规模的流行病之一，该分支已开始在欧洲野生鸟类种群中流行。这项研究使用了 1,956 种欧洲 HPAI A(H5Nx) 病毒的完整基因组来研究这种不同的流行病学轮廓期间的病毒进化。我们调查了 2020-2021 年和 2021-2022 年流行浪潮期间 A(H5Nx) 病毒传入/传出欧洲以及在欧洲内部扩散的时空模式，为传播动态和疾病流行病学的持续变化提供了证据。我们证明了流行病毒的高度遗传多样性，这些病毒经历了频繁的重配事件，首次提供了 2020-2022 年欧洲流行的多种基因型的完整概述和拟议命名法。我们描述了一种具有海鸥适应基因的新基因型的出现，该基因型为该病毒提供了占据新生态位的机会，从而推动了该疾病在欧洲野生鸟类种群中的流行。病毒重配的高度倾向、它逐渐跳跃到包括哺乳动物在内的越来越多的宿主物种，以及适应性突变的快速获得，使得在这种不断进化的情况下，病毒进化和传播的趋势难以预测。