Swayne David E
Southeast Poultry Research Laboratory, Agricultural Research Service, U.S. Department of Agriculture, 934 College Station Road, Athens, GA 30605, USA.
Avian Dis. 2007 Mar;51(1 Suppl):242-9. doi: 10.1637/7763-110706-REGR.1.
Avian influenza (AI) viruses are a diverse group of viruses that can be divided into 144 subtypes, based on different combinations of the 16 hemagglutinin and nine neuraminidase subtypes, and two pathotypes (low and high pathogenicity [HP]), based on lethality for the major poultry species, the chicken. However, other criteria are important in understanding the complex biology of AI viruses, including host adaptation, transmissibility, infectivity, tissue tropism, and lesion, and disease production. Overall, such pathobiological features vary with host species and virus strain. Experimentally, HPAI viruses typically produce a similar severe, systemic disease with high mortality in chickens and other gallinaceous birds. However, these same viruses usually produce no clinical signs of infection or only mild disease in domestic ducks and wild birds. Over the past decade, the emergent HPAI viruses have shifted to increased virulence for chickens as evident by shorter mean death times and a greater propensity for massive disseminated replication in vascular endothelial cells. Importantly, the Asian H5N1 HPAI viruses have changed from producing inconsistent respiratory infections in 2-wk-old domestic ducks to some strains being highly lethal in ducks with virus in multiple internal organs and brain. However, the high lethality for ducks is inversely related to age, unlike these viruses in gallinaceous poultry, which are highly lethal irrespective of the host age. The most recent Asian H5N1 HPAI viruses have infected some wild birds, producing systemic infections and death. Across all bird species, the ability to produce severe disease and death is associated with high virus replication titers in the host, especially in specific tissues such as brain and heart.
禽流感（AI）病毒是一组多样的病毒，根据16种血凝素和9种神经氨酸酶亚型的不同组合，可分为144个亚型；根据对主要家禽物种鸡的致死率，可分为两种致病型（低致病性和高致病性[HP]）。然而，在理解禽流感病毒复杂的生物学特性时，其他标准也很重要，包括宿主适应性、传播性、感染性、组织嗜性、病变以及疾病产生情况。总体而言，这些病理生物学特征因宿主物种和病毒株而异。在实验中，高致病性禽流感病毒通常会在鸡和其他雉科鸟类中引发类似的严重全身性疾病，并导致高死亡率。然而，这些相同的病毒在家鸭和野生鸟类中通常不会产生感染的临床症状，或者只会引发轻微疾病。在过去十年中，新出现的高致病性禽流感病毒对鸡的毒力有所增强，平均死亡时间缩短以及在血管内皮细胞中大量播散复制的倾向增加就证明了这一点。重要的是，亚洲H5N1高致病性禽流感病毒已从在2周龄家鸭中引发不一致的呼吸道感染，转变为一些毒株对多个内脏器官和脑部带有病毒的鸭子具有高度致死性。然而，与雉科家禽中的这些病毒不同，鸭子的高致死率与年龄呈负相关，雉科家禽中的病毒无论宿主年龄大小都具有高度致死性。最近的亚洲H5N1高致病性禽流感病毒已经感染了一些野生鸟类，引发全身性感染并导致死亡。在所有鸟类物种中，引发严重疾病和死亡的能力与宿主体内，尤其是大脑和心脏等特定组织中的高病毒复制滴度有关。
