PNAS：大流行流感病毒经历数年才能出现

awake

http://www.bioon.com/biology/sars/399854.shtml

在一篇与今天的猪流感担忧有关的警告性论文中，汕头大学管轶教授等发现了20世纪的3种最严重的大流行流感病毒并不是突然出现的，而且可能在它们最终暴发之前以接近完成的形式流行了许多年。这些结果可能有助于科学家和公共卫生工作者理解病毒的自然史并改善对当前病毒的监测。
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Robert Webster及其同事比较了1918、1957和1968年人类大流行流感病毒及其近亲的基因组，从而确定了它们的世系以及导致它们诞生的基因交换。这组作者发现，1918大流行流感病毒的基因很可能最早在1911年就在猪和人的身上传播，而且该病毒不太可能是从禽类传来的。这组科学家提出，全世界范围的大流行可能通过猪流感和人流感病毒的交换产生。这组作者发现，1957和1968病毒以类似的方式形成，都是通过与未知的哺乳动物宿主以及来自禽流感病毒的输入形成的。

! a) V; I  I- m- J6 p研究人员说，为了对可能的大流行进行预警，应该改变流感监测措施，从而注意血凝素基因之外的基因，甚至包括那些似乎不起眼的基因。（生物谷Bioon.com）

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PNAS July 13, 2009, doi: 10.1073/pnas.0904991106
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' j: D* k0 y8 B6 eDating the emergence of pandemic influenza viruses
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Gavin J. D. Smitha,b,1, Justin Bahla,b,1, Dhanasekaran Vijaykrishnaa,b,1, Jinxia Zhanga,b, Leo L. M. Poona, Honglin Chena,b, Robert G. Webstera,c,2, J. S. Malik Peirisa,d and Yi Guana,b,2
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4 c  k* k6 b0 c5 b3 G! Q2 R* Q) gaState Key Laboratory of Emerging Infectious Diseases & Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong SAR, China;
' b$ R& q1 q0 T/ d. y' M/ EbInternational Institute of Infection and Immunity, Shantou University, Shantou, Guangdong 515031, China;
cVirology Division, Department of Infectious Diseases, St. Jude Children's Research Hospital, Memphis, TN 38015; and
dHKU-Pasteur Research Centre, The University of Hong Kong, Pokfulam, Hong Kong SAR, China

Pandemic influenza viruses cause significant mortality in humans. In the 20th century, 3 influenza viruses caused major pandemics: the 1918 H1N1 virus, the 1957 H2N2 virus, and the 1968 H3N2 virus. These pandemics were initiated by the introduction and successful adaptation of a novel hemagglutinin subtype to humans from an animal source, resulting in antigenic shift. Despite global concern regarding a new pandemic influenza, the emergence pathway of pandemic strains remains unknown. Here we estimated the evolutionary history and inferred date of introduction to humans of each of the genes for all 20th century pandemic influenza strains. Our results indicate that genetic components of the 1918 H1N1 pandemic virus circulated in mammalian hosts, i.e., swine and humans, as early as 1911 and was not likely to be a recently introduced avian virus. Phylogenetic relationships suggest that the A/Brevig Mission/1/1918 virus (BM/1918) was generated by reassortment between mammalian viruses and a previously circulating human strain, either in swine or, possibly, in humans. Furthermore, seasonal and classic swine H1N1 viruses were not derived directly from BM/1918, but their precursors co-circulated during the pandemic. Mean estimates of the time of most recent common ancestor also suggest that the H2N2 and H3N2 pandemic strains may have been generated through reassortment events in unknown mammalian hosts and involved multiple avian viruses preceding pandemic recognition. The possible generation of pandemic strains through a series of reassortment events in mammals over a period of years before pandemic recognition suggests that appropriate surveillance strategies for detection of precursor viruses may abort future pandemics.

vilna

比较难吧？   变异能够监控，怎么知道是否会大流行？