|Home||Founder||What's New||In The News||Consulting|
Paradigm Shift Intervention Monitoring
Transmission Denial Raises Concerns
The above denial by the CDC of sustained trH3N2 transmission raises serious concerns about pandemic surveillance. Previously, the CDC has offered assurances that the trH3N2 cases did not have a common source and did not represent human transmission. However, as was noted previously, these assurances were negated by additional sequences.
One of the more telling examples was the collection in Pennsylvania, A/Pennsylvania/40/2010, that initially tested as seasonal H3N2. It was determined to be trH3N2 based on subsequent testing which included sequencing. However, the vast majority of seasonal H3N2 samples is not subjected to such additional screening and therefore would be incorrectly designated as seasonal H3N2. Most samples that are PCR tested are samples from patients linked to swine, heavily biasing the association.
The recent cases however provides the most compelling data for human transmission because the three cases from Washington County were not epidemiologically linked, but all three had the same constellation of genes including two that matched each other and an earlier isolate from Indiana. Moreover, all three sequences that were virtually identical were from cases without known contact to swine or each other.
Two of these samples have been designated as unsubtypable, which is likely linked to further evolution away from human sequences or the changing of the cutoff for designation of seasonal H3. These unsubtypable should lead to a dramatic increase in the number of trH3N2 cases reflecting sustained human-to-human transmission.
However, the identification of this transmission is blunted by the CDC’s request for samples linked to swine instead of a request for influenza A`positive samples from young patients collected in the off season, as was the case for the four recent confirmed cases, all of which were under 10 years of age.
The focus on swine linked cases and the reliance on a heavily biased surveillance system that has failed to identify the sources for the recent cases, raises concerns that the CDC is not committed to serious testing unrelated to the unsupported position that trH3N2 is not transmitting in a sustained manner.