Zoonotic infections are one of the great disease risks of our lifetime.  Our “cousin” the pig is one of the likely characters in a pandemic story.  So it is with some anxiety that I read the story in recent ProMed posting about a recent study that revealed that more than 80 percent of pigs that tested positive for influenza A virus at Ohio county fairs between 2009 and 2011 showed no signs of illness.  Great!!!

Butler County Fair6
Ohio State University researchers tested 20 pigs each at 53 fair events over those 3 summers and found at least one flu-positive pig at 12 fairs — almost a quarter of fairs tested.

The influenza strains identified in pigs in this study include H1N2 and H3N2 viruses — strains that have been circulating in pigs since 1998. In 2011, all of the H3N2 and H1N2 isolates found in pigs at the fairs contained a gene from the 2009 pandemic strain of H1N1, which is similar to the H3N2v strain causing human illness this year.

So let me get this straight…we have asymptomatic but sick pigs interfacing with people of all kinds at local and state fairs.  Shouldn’t I be worried?!?! The lead researcher quickly went on to say that though this finding alone is no cause for panic, it does show how quickly influenza viruses can change. A second study led by Bowman, researchers compared the genomic sequences of influenza A viruses recovered in July 2012 from pigs and people. The analysis, showing a greater than 99 percent genetic similarity among the viruses, confirms that pigs and humans were infected with the same virus, indicating interspecies transmission.

I know he said don’t worry…but I don’t know about that!?!?!?!?!

Remember that the CDC had confirmed 107 human cases of H3N2v influenza in Ohio since July 2012, with the majority linked to exposure to pigs at agricultural fairs (as of 25 Sep 2012). While most of the human illness caused by H3N2v has been mild, one person, who had a compromised immune system, has died. The more often that flu viruses are transmitted, the better their chances are of evolving into a strain which humans are not immune, which is the big-picture concern among scientists monitoring these viral infections.

Pigs are like a blank canvas and they can be infected with human, avian and swine-origin influenza viruses, making it possible for these viruses to easily swap their genetic material, which could of course allow for a new strain to emerge.  The lead researcher went on to say that the potential is there for newly emerged strains to be the next pandemic we never saw coming.

Isn’t this the guy that said, but don’t worry?!?!?!.