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Commentary
More Swine
Match Failures With Novel 2011 Human trH3N2
Recombinomics Commentary 11:30
November 14, 2011
However, these newly released sequences reflect an increased surveillance for SOIV (swine origin influenza virus) and strongly suggest that the prior sequences released by the same group, which included trH3N2 isolates as well as isolates as recent as July, 2011 represented the closest matches to the human isolates. However, all were clearly distinct from the seven 2011 human trH3N2 isolates which match each other in all 8 gene segments. Moreover, this novel constellation has not been reported in swine anywhere in the word, in spite of increased swine surveillance.
Eventually the novel constellation will be found in swine because human triple reassortants can infect swine as was seen for H1N1pdm09. However, like the 2011 trH3N2 constellation, matching isolates were not identified in swine infections prior to the human isolates, and the collection dates of the recent sequences from Iowa State indicate the novel constellation will not be found in swine isolates from samples collected prior to July 2011, which is in marked contrast to the human isolates, where all seven isolates, from 3 states (Indiana, Pennsylvania, Maine) collected over 3 months (July – October) have the same novel constellation, which evolved from human 2010 isolates.
The human cases have been identified through a heavily biased surveillance system, which prioritizes samples with swine “exposure” and discounts samples without a swine link. The bias has generated media reports claiming that the novel isolates are due to infection from associated swine, even though none of the swine associated with the human cases have been symptomatic and no SOIV has been isolated from the associated swine. The media reports have been parroted by ProMED, in comments which are not scientifically based. Consequently, the claims of swine origin for the confirmed human cases are little more than unsupported speculation.
Moreover, the CDC has continued to bias its sampling as seen by the sub-typing of only one of the thirty-two influenza A samples from Region 4 collected in the 2011/2012 season.
Expanded trH3N2 testing of influenza A samples with no swine contact, facilitated by distribution of appropriate PCR kits to state labs is long overdue.
2011 Isolates With Collection Date
H1N1
A/swine/Illinois/A01049980/2011 05/17
A/swine/Illinois/A01049981/2011 05/17
A/swine/Iowa/A01202023/2011 05/26
A/swine/Iowa/A01202033/2011 05/27
A/swine/Iowa/A01202034/2011 05/27
A/swine/Iowa/A01202041/2011 06/02
A/swine/Iowa/A01202048/2011 06/02
A/swine/Iowa/A01202049/2011 06/02
A/swine/Iowa/A01202056/2011 06/02
A/swine/Mississippi/A01202059/2011 06/08
H1N2
A/swine/Iowa/A01049970/2011 05/16
A/swine/Michigan/A01202035/2011 05/26
A/swine/Michigan/A01202036/2011 05/26
A/swine/Michigan/A01202037/2011 05/26
A/swine/Iowa/A01202063/2011 06/07
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