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Maine CDC Requests Influenza A Positive Samples
Recombinomics Commentary 19:00
October 27, 2011

Swine-Origin Novel Influenza A Case in Maine: Maine CDC Recommendations for Healthcare Providers

Please report any cases of laboratory positive influenza to Maine CDC by fax (1-800-293-7534) or by phone through our 24 hour Disease Reporting and Consultation Hotline (1-800-821-5821). All influenza A rapid positive tests should be confirmed by PCR.

The above request by the Maine CDC to area Healthcare Providers requests samples from influenza A positives.  It goes beyond the earlier request by the US CDC for samples from patients with flu-like symptoms who have a swine exposure.  The broader Maine request indirectly acknowledges the fact that although all confirmed 2011 trH3N2 have some sort of rather loose swine “exposure”, the identities between all 5 2011 trH3N2 sequences, including the presence of an M gene segment from H1N1pdm09 (pandemic H1N1) which was “critical" for the jump of H1N1pdm09 from swine to human, is compelling evidence of human transmission in the absence of a swine “exposure”.

The swine “exposure” is less than convincing for swine transmission.  The constellation of flu genes in all five 2011 human trH3N2 cases has yet to be found in any reported swine sequence in spite of increased swine surveillance in the US and worldwide.  Moreover, the “exposure” for the five US case weak.  The Indiana case had no direct exposure.  His caretaker was exposed to swine but the caretaker and associated swine were asymptomatic and there have been no reports of confirmed SOIV in the swine or the caretakers (as well as no reports of trH3N2 and/or trH3N2 with the constellation of genes found in all five confirmed cases).  The absence of symptoms or infections associated with the Indiana case also applies to the more recent cases from Pennsylvania and Maine, which involve visits to agricultural fairs (Washington County in PA and Cumberland County in ME) that exhibited asymptomatic swine with no confirmed influenza infections.

The request for PCR may also signal an approach for the identification of trH3N2 cases via a ratio between tests for influenza A (which can be quantified with a PCR test) and tests for human H3.  Thus, samples which give strong positives for influenza A but weak positives for human H3 may be as predictive for trH3N2 as tests that are influenza A positive and negative for H3 (and H1). 

State labs currently do not have a direct test for swine H3.  Thus, as was seen early in the H1N1 pandemic in 2009, state labs send samples that are influenza A positive but negative for H3 and H1 to the CDC for trH3N2 confirmation (via a PCR test targeting swine H3, and/or sequencing of the sample), as was done for the five cases confirmed in 2011.

Normally, these samples would be designated unsubtypables (or unable to subtype), but the bizarre reporting of the Pennsylvania cases and the absence of reporting of the Indiana and Maine cases in the sub-typing figures and tables, has raised concerns that the CDC is playing a shell game with these cases, as additional trH3N2 cases without swine exposure are under epidemiological investigation.

An explanation for the bizarre sub-type reporting of trH3N2 cases, and the distribution of PCR kits for swine H3 to state labs is long overdue.

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