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No Thought On
trH3N2 Transmission Raises Concerns
Sears said there is no thought at this point that the virus is spreading from person to person and there were no reports of flu among members of either child's family.
The above comments from a Maine CDC epidemiologist provide insight into the lack of reported trH3N2 cases without swine contact. The above comments follow the report of the second trH3N2 case in Maine in October, which is in addition to the October case in Indiana. All three cases have the same constellation of flu genes which also match the earlier 2011 cases in Pennsylvania and Indiana, leaving little doubt that this novel human contagion, which has never been reported in swine, is transmitting in humans.
However, detection requires submission of samples to the CDC because this is no commercial test for trH3N2, and states also do not have an assay for the novel pathogen. States rely on an absence of activity for H1 and H3 on influenza A positive samples. However, in the past trH3N2 isolates have been positive for seasonal H3, limiting detection. 2011 cases have been reported as inconclusive in sub-typing tests and two were designated as “unable to sub-type” in CDC FluView reports, but these reports have been inconsistent, raising concerns that cut-off values for PCR testing have been adjusted.
Thus, many states continue to rely on a prior swine exposure to flag samples for further testing at the CDC. Moreover, in the early release MMWR describing the first two 2011, the CDC requested samples from patients with swine exposure, limiting the number of samples and heavily biasing testing. This bias was clear in the Maine CDC advisory, which claimed that all prior 2011 trH3n2 cases had swine contact, which was not true for the first Indiana case. Moreover, the Indiana DoH week 43 report claimed that no novel influenza was circulating in the state, when they were reporting the second trH3N2 case. Moreover, the week 43 case was the only PCR positive influenza case in week 43, and only the second case for the 2011/2012 flu season. Thus, the claim of no novel influenza circulating in humans in Indiana was false, as was the Maine CDC claim of swine exposure for all 2011 trH3N2 cases.
Remarkably, neither Maine nor Indiana has identified a source for the four trH3N2 cases reported in those states, and Pennsylvania has not identified a source for the three earlier cases in Washington County. None of the swine were symptomatic and no SOIV has been reported in those three states, and a constellation of the genes found in the seven human cases has not been reported in any swine anywhere in the world.
Thus, the absence of thought on human transmission in Maine, and the limited testing in Indiana, has heavily biased testing away from those without swine contact. This approach appears to have affected investigation of pneumonia cases in elementary on middle school students in Shelby County, Indiana. This age group is at risk for trH3N2 infections and the media descriptions match those of trH3N2 (high fever and lack of response to antibiotics). However, the state is sending out Mycoplasma test kits, even though such cases are mild and produce a low grade fever, in contrast to the high fevers seen in the Indiana children, including the five who have been hospitalized.
The lack of thought on human transmission of trH3N2, as reported in recent media and ProMED comments, continues to raise pandemic concerns.