此研究的結論並未偏離稍早之前由墨西哥國立自治大學（National Autonomous University of Mexico）的納瓦（Gerardo Nava）教授和同僚發表在網路期刊Eurosurveillance的研究報告，該研究最早經由病毒序列的比對指出：這個病毒最可能是從近代豬病毒演化而來；這個發現顯示，北美洲養豬在這個病毒衍生和維持上，可能扮演要角；且文中直言豬隻成為A型（H1N1）流感病毒『混合管道』的角色，在10多年前就已存在，然而，決策者和科學界似乎低估這個風險；除此之外，該文並同時強調：「問題不在於病豬會死或甚至會把病毒傳給人。問題在於病毒正在（病豬體內）重組，產生新序列、新基因。」
美國的CDC也曾發現，在加州有少數病例早於墨西哥宣告爆發豬流感，但未能查出其源頭。《華爾街日報》報導：在加州發現的首宗病例，是來自與墨西哥邊界毗鄰的聖迭戈縣的10歲男孩，他3月30日發病，墨西哥當時還未爆發疫情；第2宗病例是來自加州鄰縣的9歲女孩，她3月28日因咳嗽與發高燒掛診。這兩個案例之前不曾前往墨西哥，也不曾接觸豬隻。上述研究成果有助於美國加州病例的比對。
埃及本週三又傳出3起新流感確診病例，使當地的確診病例增至15起；為防範豬流感持續蔓延，埃及政府宣布下周殺光全國豬隻，至目前為止，埃及已經撲殺了一萬五千頭豬。由於先前世界衛生組織(WHO)多次宣布新流感與豬隻無關，但埃及方面仍堅持要撲殺全國所有的豬隻，已經引起引發外界的抨擊，法國前豔星碧姬芭杜更致函埃及總統穆巴拉克，要求停止撲殺行為，但埃及方面仍無動於衷。現在此研究等於證明埃及政府具有遠見。
台灣應該展開對豬隻的流感偵測，作為防疫的一環。
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英文原文
Letter
Nature advance online publication 11 June 2009 | doi:10.1038/nature08182; Received 24 May 2009; Accepted 4 June 2009; Published online 11 June 2009
Origins and evolutionary genomics of the 2009 swine-origin H1N1 influenza A epidemicnear-final version
Gavin J. D. Smith1, Dhanasekaran Vijaykrishna1, Justin Bahl1, Samantha J. Lycett2, Michael Worobey3, Oliver G. Pybus4, Siu Kit Ma1, Chung Lam Cheung1, Jayna Raghwani2, Samir Bhatt4, J. S. Malik Peiris1, Yi Guan1 & Andrew Rambaut2
- State Key Laboratory of Emerging Infectious Diseases & Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, 21 Sassoon Road, Pokfulam, Hong Kong SAR, China
- Institute of Evolutionary Biology, University of Edinburgh, Ashworth Laboratories, King's Buildings, Edinburgh EH9 3JT, UK
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona 85705, USA
- Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK
Correspondence to: Yi Guan1Andrew Rambaut2 Correspondence and requests for materials should be addressed to A.R. (Email: a.rambaut@ed.ac.uk) or Y.G. (Email: yguan@hku.hk).
This article is distributed under the terms of the Creative Commons Attribution-Non-Commercial-Share Alike licence (http://creativecommons.org/licenses/by-nc-sa/3.0/), which permits distribution, and reproduction in any medium, provided the original author and source are credited. This licence does not permit commercial exploitation, and derivative works must be licensed under the same or similar licence.
In March and early April 2009, a new swine-origin influenza A (H1N1) virus (S-OIV) emerged in Mexico and the United States1. During the first few weeks of surveillance, the virus spread worldwide to 30 countries (as of May 11) by human-to-human transmission, causing the World Heath Organisation to raise its pandemic alert to level 5 of 6. This virus has the potential to develop into the first influenza pandemic of the twenty-first century. Here we use evolutionary analysis to estimate the timescale of the origins and the early development of the S-OIV epidemic. We show that it was derived from several viruses circulating in swine, and that the initial transmission to humans occurred several months before recognition of the outbreak. A phylogenetic estimate of the gaps in genetic surveillance indicates a long period of unsampled ancestry before the S-OIV outbreak, suggesting that the reassortment of swine lineages may have occurred years before human emergence, and that the multiple genetic ancestry of S-OIV is not indicative of an artificial origin. Furthermore, the unsampled history of the epidemic means that the nature and location of the genetically closest swine viruses reveal little about the immediate origin of the epidemic, despite the fact that we included a panel of closely related and previously unpublished swine influenza isolates. Our results highlight the need for systematic surveillance of influenza in swine, and provide evidence that the mixing of new genetic elements in swine can result in the emergence of viruses with pandemic potential in humans2.
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