North American flu season could be complicated with H3N2 virus

Posted Sep 28, 2009 by Michael Krebs
With mass media attention circulating around the worldwide H1N1 pandemic, little focus has been put on this season's more virulent flu variety found in the H3N2 bug. The presence of both varieties could make for a complicated flu season.
Microscopic image of Swine Flu
Microscopic image of Swine Flu
While the H1N1 swine flu virus has captured headlines for its debut as a worldwide pandemic, researchers and health officials are now starting to turn their attention to a particularly nasty strain of influenza virus that is also making the rounds and could help formulate a considerably more complicated and dangerous North American flu season this fall and winter. This second viral strain is catalogued under the H3N2 family of viruses - and unlike the H1N1 varieties, the H3N2 bugs typically cause more severe symptoms and complications.
"This season is going to be crazier than ever," William Schaffner, an infectious-disease expert at Vanderbilt University, told The Wall Street Journal.
H3N2 has been in circulation for some time, but laboratory experts working out of the World Health Organization are beginning to see increases in a new more aggressive variant among overall H3N2 viral species distribution and global composition. H3N2 is particularly dangerous for elderly populations, and this new variant poses an interesting augmentation to the H1N1 strain that has a lesser impact on older demographics.
The new H3N2 variant makes up only 5 percent of current H3N2 influenza viruses in circulation within the United States - however, flu behaviors and distribution are notoriously unpredictable.
Given this, WHO influenza experts are now suggesting that northern hemisphere countries may be facing a seasonal vaccination mismatch.
"The predominant H3N2 virus circulating at the moment is not that contained in the Northern Hemisphere vaccine," Gregory Hartl, a spokesperson for the World Health Organization, told the Canadian Press.
With both H1N1 and H2N3 in broad circulation, scientists are concerned that the northern hemisphere flu season could be particularly nasty and drawn out. There are indications that the H1N1 pandemic strain is crowding out other H1N1 varieties, and this activity has positive public health implications - as the more populous H1N1 pandemic strain offers mild symptoms. It is unclear whether or not the H1N1 pandemic strain will also push out the H3N2 varieties that are of most concern.