Three separate articles offer an explanation for the origin of H1N1 (Brockwell-Staats et al., 2009; Kingsford et al., 2009; Smith et al., 2009). The explanation is based on facts, including gene sequences of previously known influenza viruses. While it is possible that H1N1 was engineered, there is no direct evidence of this. The best explanation for H1N1 is a natural origin.

One virologist, Adrian Gibbs, hypothesized that H1N1 escaped from a lab. He has stated that he is uncertain of this and that it is simply a plausible hypothesis. The WHO has responded that the hypothesis does not stand to scrutiny (Hitt, 2009).

Brockwell-Staats C, Webster RG, Webby RJ. (2009) Diversity of Influenza Viruses in Swine and the Emergence of a Novel Human Pandemic Influenza A (H1N1). Influenza Other Respi Viruses. 3: 207 – 213.
[PMID: 19768134]

Hitt E. (May 14, 2009) Novel H1N1 Flu a Naturally Circulating Virus, Not From a Laboratory. Medscape Medical News.
[http://www.medscape.com/viewarticle/702862]

Kingsford C, Nagarajan N, Salzberg SL. (2009) 2009 Swine-origin influenza A (H1N1) resembles previous influenza isolates. PLoS One. 4: e6402.
[http://www.plosone.org/article/info:doi%2F10.1371%2Fjournal.pone.0006402]

Smith GJ, Vijaykrishna D, Bahl J, Lycett SJ, Worobey M, Pybus OG, Ma SK, Cheung CL, Raghwani J, Bhatt S, Peiris JS, Guan Y, Rambaut A. (2009) Origins and evolutionary genomics of 2009 swine-origin H1N1 influenza A epidemic. Nature. 459: 1122 – 1125.
[http://www.nature.com/nature/journal/v459/n7250/pdf/nature08182.pdf]

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A simple summary of the three articles offering an explanation for 2009/H1N1′s natural origin follows.

Influenza A virus genome consists of 8 negative sense ssRNA segments: M, NA, PB1, PB2, PA, NP, NS and HA. Influenza viruses change by reassortment, which occurs when two different influenza viruses infect one cell and RNA segments are mixed. Pigs are thought to be reassortment vessels for influenza because they can be infected by swine, avian and mammalian strains (Webster et al., 1992).

Pandemic 2009/H1N1 resulted through reassortment between Eurasian swine H1N1 (ES-H1N1) and triple reassortment swine H1N2 (TRS-H1N2). The M and NA segments came from the ES-H1N1 and other 6 came from TRS-H1N2.

TRS-H1N2 has been circulating in North America since 1998. It has PB1 and NA segments from human H3N2 influenza; PA and PB2 segments from avian influenza; NP, M, NS and HA segments from classical H1N1 swine influenza. When ES-H1N1 and TRS-H1N2 reassorted, the M and NA segments from H1N1 were packaged with the six other segments from H1N2. 2009/H1N1 is this new 2+6 ‘package’ of gene segments.

Webster RG, Bean WJ, Gorman OT, Chambers TM, Kawaoka Y. (1992) Evolution and ecology of influenza A viruses. Microbiol Rev. 56: 152 – 179.
[http://mmbr.asm.org/cgi/reprint/56/1/152.pdf]