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trH3N2 Swine Close Contact Media Myth
Recombinomics Commentary 21:00
November 28, 2011

Another influenza strain has appeared in the United States. Cases are limited, and most are associated with direct contact with pigs. Cases spread from person to person remain limited. The virus is a swine-origin triple-recombinant H3N2 that includes the matrix gene from the 2009 H1N1 virus.

As of yesterday, 10 cases have been counted in Pennsylvania, Maine, Indiana, and Iowa.

From: CIDRAP News, Nov 22, 2011

Roger Miller, MD (OSU Student Health Services)

The above comments are from an announcement from Ohio State University Student Health Services, representing the accelerating spread of mis-information on the novel trH3N2.  Cited is the CIDRAP News November 22 release which noted the linkage of earlier 2011 cases with swine, including "close contact."

The CDC uses a very loose definition of “swine exposure”, including the first case reported for the novel trH3N2, A/Indiana/08/2011, who was said to have “indirect exposure” to swine because his caretaker had exposure to swine in the weeks prior to his symptoms.  However, the swine were asymptomatic, as was the caretaker and her family members, and no novel trH3N2 has been identified in any swine in Indiana, in spite of two human cases (A/Indiana/10/2011 from a veterinarian developing symptoms 3 months after the above cases), which were investigated by the Indiana Board of Animal Health.  Similarly, Pennsylvania and Maine departments of agriculture investigated swine linked to confirmed cases in those states failed to identify trH3N2 in any swine.  Moreover,  the USDA enhanced surveillance which has identified dozens of swine triple reassortant infections in 2011, and a larger number in 2010, has failed to identified novel trH3N2 in any sample collected prior to the July / August cases in Indiana and Pennsylvania, and the only reported example in swine is a September 13 collection from a pig in New York,

In the latest CDC “Have You Heard’ claims of “reported” trH3N2 in swine in several states were made, but the only reported match in Genbank or GISAID is the recently released sequence from New York,  The release of sequences for all eight gene segments and the absence of sequences from other isolates suggests it is the only match found by the USDA.  However, the claim in the Nov 22 "Have You Heard" and comments in the Helen Branswell piece on matches in “pigs in the US Midwest” may signal one or more additional examples.  However, these unpublished sequences are increasingly likely to be samples collected after the human cases in Indiana and Pennsylvania, which is expected because the human cases strongly suggest the novel trH3N2 is widespread in people.  Therefore, jumps back to swine, and detection in collections after the July/August human cases, are expected.

However, the CDC has cited its heavily biased testing of those with swine contact, to create an illusion of linkage with swine exposure and human infections.  This linkage is supported by limited testing of those without swine contact.  Thus, in Maine there are only two confirmed cases, and both are trH3N2 and in Indiana there are only three cases, and two are trH3N2.  Thus, more testing of cases without swine exposure is needed, including the large number of influenza A positive samples which have not been sub-typed.

The CDC’s “swine exposure” linkage for trH3N2 cases is frequently converted into “swine contact” media statements, which limits testing and feeds the heavily biased testing focusing on those with swine contact, in spite of the large cluster in Iowa with lab confirmed novel trH3N2 in the absence of swine exposure, and clear human to human transmission to lab confirmed and symptomatic contacts.

Thus, the limited testing leads to claims of no sustained human transmission, when the sequence identities between the 10 human cases leave little doubt that the novel trH3N2 has been transmitting efficiently in many US states and has been doing so for many months.

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