# 5934
Reassortant H3N2 virus detected in Pennsylvania,Indiana & Maine – Source CDC
Although it doesn’t seem to happen terribly often, every once in awhile an avian or swine influenza virus manages to infect a human host.
Usually after direct close contact with a bird or or pig.
This is a pattern we’ve seen with the avian H5N1, H9N2, and H7N7 viruses, and we’ve also seen it a couple of dozen times since 2005 with SOIV (swine origin influenza virus) trH1N1 and trH3N2 strains.
Most of the time, these infections turn out to be dead end transmissions, as the virus is only partially adapted to human physiology.
Occasionally, we’ve seen evidence of limited secondary transmission albeit not in a sustained and efficient manner.
A recent `exception to this rule’ was the 2009 H1N1 pandemic virus, which after bouncing around in the swine population for years, finally evolved into an easily transmissible human pathogen.
If it were an easy thing for viruses to do, we’d be hip deep in pandemic viruses all of the time. It apparently takes a lot of evolutionary trial and error before a virus can `get it right’.
Although few of these avian and swine viruses have adapted well enough over the years to pose a serious public health threat, we watch them with great interest because the potential exists for them to eventually `figure us out’.
Over the past 90 days or so, we’ve been keeping up with a new SOIV virus has been detected among a small handful of people across three states. This virus is a reassortment of a swine trH3N2 and the 2009 pdmH1N1 virus.
You can find earlier coverage of these cases in A 5th trH3N2 SOIV Report & CDC Update On trH3N2 Cases.
Today the state of Maine’s website has news of their 2nd case detected during the month of October. It can be found in their weekly influenza surveillance report dated November 1st.
Novel Influenza A Virus
• Maine confirmed a second case of swine origin novel influenza A virus. The first case was confirmed on October 17th , and the second case was confirmed October 31st. Both cases had multiple exposures to pigs.
These cases are the 5th and 6th recognized cases of human infection with S-OtrH3N2 with the M segment gene from the pH1N1virus.
More information can be found in a Health Alert, released 10/19/2011 accessible through: http://www.maine.gov/tools/whatsnew/attach.php?id=313425&an=1.
Epidemiological investigations into these cases continue.
While sporadic cases such as these are not particularly alarming, we do watch these infrequent viral escapees from the farm for signs of adaptation.
As long as they are not able to transmit efficiently among humans they pose a very low public health threat.
The concern is that the odds favor that the next pandemic virus will come from a farm – where large numbers of animals intermingle, swap viruses, and come in daily contact with humans.
Which is why so many scientists are calling for more comprehensive testing and surveillance on farm animals.
For more on the reassortment potential of avian, swine, and human flu viruses, you can’t do better than Helen Branswell’s excellent Scientific American article from last December called Flu Factories, or her SciAm Podcast interview.
For some of my earlier posts on this newly discovered trH3N2 swine flu virus, you may wish to revisit:
MMWR: Swine-Origin Influenza A (H3N2) Virus Infection in Two Children
