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H1N1 (Swine Flu): Human Infection with a Pandemic H1N1 and Seasonal H1N1 Flu Reported from Canada in Three Workers

March 8, 2010

Reported in current issue of The Journal of Infectious Disease, is an interesting report from Canada and clearly demonstrates several principals that we already know but probably need to be reminded of:

  • Vigilance is essential with influenza.  Ongoing global surveillance is critical.
  • Reassortment is always possible and the virus can change literally at any moment.
  • Humans working in close proximity to “signature” animals known for disease transference and mixing (pigs, ferrets, birds) allow infinite opportunities for reassortment.

Last fall, a reassortant influenza A(H1N1) virus of swine origin distinct from the pandemic H1N1 2009 strain was isolated from 3 patients, all of whom worked at the same large hog operation in Saskatchewan, Canada.

Artist Rendering of Reassortment - Take Two Viruses, Combine in the Cell in the Nucleus and Bingo - New Virus!

The genomic composition of the isolates has not been previously reported, to the author’s knowledge, and was the product of a genetic reassortment between seasonal H1N1 and triple‐reassortant influenza virus that emerged in North American swine during the late 1990s. The neuraminidase and hemagglutinin genes of A/Saskatchewan/5350/2009, A/Saskatchewan/5351/2009, and A/Saskatchewan/5131/2009 were derived from human H1N1 virus and were closely related to those of A/Brisbane/59/2007.

This is an excellent example of the need for continual and ongoing observation with the virus influenza.  This type of reassortant often occurs and goes nowhere as may be the case in these three workers.  Or it could be the beginning of the evolution of the virus into something else…just like what we witnessed in Mexico in 2009.  We have been fortunate to date that the current pandemic H1N1 illness has been mild….the next reassortant may not be so kind.

If you are interested in reading about reassortment, I recommend to you the writings of Vincent  Racaniello at the Virology Blog.  He is brilliant, an incredible writer and he makes all of this complicated information actually pretty easy to understand! Check out this article Reassortment of the Influenza Virus Genome” http://www.virology.ws/2009/06/29/reassortment-of-the-influenza-virus-genome/

http://www.journals.uchicago.edu/doi/abs/10.1086/651507

ProMED Digest V2010 #104

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