Origin and Evolution of Influenza Viruses

为提供资料，说明甲型流感病毒如何在北部地区筑巢地区的水禽水库中存活，以及病毒在自然界中持续存在的机制，阿拉斯加在1993年至1994年的夏季禽流感繁殖期继续进行病毒学监测。然后对分离株的基因进行了系统发育分析。流感病毒主要从阿拉斯加中部地区筑巢的涉水鸭子的粪便样本中分离到。从541份鸭的粪便中分离到33株流感病毒和15株副粘病毒。流感病毒亚型由23个H3N8、8H4N61H2N3和1H7N3组成。连同我们先前的监测研究的结果，以及在1991年和1992年获得文部科学研究资助03041013资助的研究结果，从粪便样本中分离出的流感病毒总数为108株，其中包括1株H 2N3，37 H…3N8、55株H4N6、1H7N3、1株H8N2、1株H10N2、11株H10N7、1株H10N9。这些结果表明，在阿拉斯加中部主要养殖区的鸭子种群中，流感病毒一直保持不变，不同亚型的甲型流感病毒共存。从鸭子筑巢的湖水样本中也分离到流感病毒。即使在1994年秋天，当它们去南方迁徙时，仍然从湖水中分离出病毒。本研究结果支持流感病毒在水禽种群中通过水媒传播的观点，并揭示了病毒在其繁殖的湖泊中逐年延续的机制。对代表性分离株的NP和H3 HA基因的系统发育分析表明，它们属于禽流感病毒的北美谱系，表明阿拉斯加中部繁殖的大部分水禽迁徙到北美而不是亚洲。因此，对水禽不同分离株的系统发育分析使推测携带病毒的寄主鸟类的迁徙飞行成为可能。较少

To provide information how influenza A viruses are maintained among waterfowl reservoirs at their nesting areas in the northern territory and on the mechanism of perpetuation of the viruses in nature, virological surveillance of avian influenza was continued in Alaska during their breeding season in summer from 1993 to 1994. Phylogenetic analyzes of the genes of the isolates were then carried out.Influenza viruses were isolated mainly from fecal samples of dabbling ducks in their nesting places in central Alaska. From 541 fecal samples of ducks, 33 influenza viruses and 15 paramyxoviruses were isolated. The numbers of subtypes of influenza viruses consisted of 23 H3N8,8H4N61H2N3, and 1H7N3. Together with the results of our previous surveillance study, which was also supported by Grant-in-Aid for Scientific Research 03041013 by the Ministry of Education, Science and Culture in 1991 and 1992, the total number of influenza virus isolates from fecal samples is 108 comprising of 1 H2N3,37 H … More 3N8,55 H4N6,1H7N3,1 H8N2,1 H10N2,11 H10N7, and 1 H10N9 strains. These results indicate that influenza viruses have been maintained in duck population in the major breeding areas of central Alaska and that different subtypes of influenza A virus cocirculate.Influenza viruses were also isolated from water samples of the lakes where the ducks nest. Even in autumn of 1994 when they had left for migration to south, viruses were still isolated from the lake water. The present results support the notion that influenza viruses have been maintained in waterfowl population by water-borne transmission and revealed the mechanism of year by year perpetuation of the viruses in the lakes where they breed.Phylogenetic analysis of the NP and H3 HA genes of the representative isolates showed that they belong to the North American lineage of avian influenza viruses, suggesting that the majority of the waterfowls breeding in central Alaska migrate to North America and not to Asia. Thus phylogenetic analysis of various isolates from waterfowls made it possible to presume the migratory flyways of host birds carrying viruses. Less