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Unformatted text preview: T h e new england journal o f medicine n engl j med 361;3 nejm.org july 16, 2009 279 review article Current Concepts Historical Perspective Emergence of Influenza A (H1N1) Viruses Shanta M. Zimmer, M.D., and Donald S. Burke, M.D. From the School of Medicine (S.M.Z.) and the Graduate School of Public Health (D.S.B.), University of Pittsburgh, Pitts- burgh. Address reprint requests to Dr. Burke at the Graduate School of Public Health, University of Pittsburgh, 130 De- Soto St., Rm. 624, Pittsburgh, PA 15261, or at email@example.com. This article (10.1056/NEJMra0904322) was published on June 29, 2009, at NEJM.org. N Engl J Med 2009;361:279-85. Copyright 2009 Massachusetts Medical Society. O n April 17, 2009, officials at the Centers for Disease Control and Prevention (CDC) confirmed two cases of swine influenza in children living in neighboring counties in California. 1 Here we take a perspective from systems biology to review the series of evolutionary and epidemiologic events, starting in 1918, that led to the emergence of the current swine-origin influenza A (H1N1) strain (S-OIV), which is widely known as swine flu. This article is one of two historical articles on influenza A (H1N1) viruses in this issue of the Journal. 2 Our review focuses on the key steps that characterize this viral evolution (Fig. 1). Emergence of a VIrus Simultaneous Appearance in Humans and Swine (1918) Before 1918, influenza in humans was well known, but the disease had never been described in pigs. 3 For pig farmers in Iowa, everything changed after the Cedar Rapids Swine Show, which was held from September 30 to October 5 of that year. 4 Just as the 1918 pandemic spread the human influenza A (H1N1) virus worldwide and killed 40 million to 50 million people, herds of swine were hit with a respiratory ill- ness that closely resembled the clinical syndrome affecting humans. Similarities in the clinical presentations and pathologic features of influenza in humans and swine suggested that pandemic human influenza in 1918 was actually adapted to the pig, and the search for the causative agent began. 5,6 The breakthrough came in 1931 when Robert Shope, a veterinarian, transmitted the infectious agent of swine influenza from sick pigs, by filtering their virus- containing secretions, to healthy animals. 7 Infectivity of the filtrate was subse- quently confirmed by Smith, Andrewes, and Laidlaw, 8 who used the ferret model of influenza infection to document transmissibility for both human and swine viruses. Shope furthered the notion that the human pandemic strain of influenza A (H1N1) and the infectious agent of swine influenza were closely related by showing that human adult serum could neutralize the swine flu virus....
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This note was uploaded on 01/06/2010 for the course NS 2750 taught by Professor Haas&gu during the Spring '08 term at Cornell University (Engineering School).
- Spring '08