Influenza A viruses (IAVs) are the causative agents of one of the most important viral respiratory diseases in pigs and humans. Human and swine IAV are prone to interspecies transmission, leading to regular incursions from human to pig and vice versa. This bidirectional transmission of IAV has heavily influenced the evolutionary history of IAV in both species. Transmission of distinct human seasonal lineages to pigs, followed by sustained within-host transmission and rapid adaptation and evolution, represent a considerable challenge for pig health and production. Consequently, although only subtypes of H1N1, H1N2, and H3N2 are endemic in swine around the world, extensive diversity can be found in the hemagglutinin (HA) and neuraminidase (NA) genes, as well as the remaining six genes. We review the complicated global epidemiology of IAV in swine and the inextricably entangled implications for public health and influenza pandemic planning.

中文翻译：

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猪甲型流感病毒与人类的纠结关系

甲型流感病毒（IAV）是猪和人中最重要的病毒性呼吸道疾病之一的病原体。人和猪的IAV容易发生种间传播，导致从人到猪的定期入侵，反之亦然。IAV的这种双向传播严重影响了两个物种中IAV的进化历史。不同的人类季节性谱系向猪的传播，接着在宿主内部的持续传播以及快速的适应和进化，对猪的健康和生产构成了巨大的挑战。因此，尽管在世界各地的猪中只有H1N1，H1N2和H3N2的亚型是地方性的，但在血凝素（HA）和神经氨酸酶（NA）基因以及其余六个基因中可以发现广泛的多样性。