SIV Surveillance Results

June 21, 2012 — 

[The following was excerpted from a very informative article in National Hog Farmer describing the evolution of influenza in swine.]
The ISU-VDL has received more than 2,000 samples from 22 states for SIV surveillance. Samples submitted from Iowa, Minnesota, Indiana, Illinois, North Carolina and Nebraska account for approximately 86% of samples. All influenza isolates have been subtyped H1N1, H1N2, H3N2 or mixed infections. Among H1 viruses, 13% had 2009 novel pandemic H1N1 virus (H1N1pdm09) HA, NA and M genes (HA-Hemagglutinin, NA-Neuraminidase, and M-Matrix). Remarkably, an additional 49% of other H1 viruses had incorporated the M gene from H1N1pdm09.Among H3 viruses, 46% contained the H1N1pdm09 M gene.

This demonstrates that the H1N1pdm09 virus is co-circulating in U.S. swine, resulting in reassortant viruses with endemic H1N1, H1N2 and H3N2 swine viruses.

In the fall of 2011, an H3N2 variant virus emerged, resulting in 13 human infections in Indiana, Maine, Pennsylvania, Iowa, Utah and West Virginia. Sequencing of these H3N2v from human cases revealed that the M gene was from the H1N1pdm09 virus, but HA and NA genes were from endemic H3N2 swine influenza viruses. This particular combination of influenza genes had not been previously detected in humans.

ISU-VDL surveillance sequence data indicates a virus with HA, NA and M genes closely related to the human H3N2v virus was detected in the swine population as early as Aug. 22, 2011. Similar H3N2 viruses have been detected at the ISU-VDL from Iowa, Indiana, Illinois, Ohio and North Carolina swine since that time.

Please visit National Hog Farmer, June 19, 2012 for the complete article.