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Commentary
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in Seasonal H1 Raises Pandemic Concerns
Recombinomics
Commentary 16:58
October 31, 2010
The most dramatic rise in seasonal H1 was in Texas, where all five sub-typed influenza A samples were H1, but 4/5 were seasonal H1. None of the recent seasonal H1 reports have disclosed antigenic or sequence analysis of these samples. There are only three 2010 seasonal H1N1 sequences at GISAID and all three were from China collected in early 2010 (two were Brisbane/59-like and had H274Y, while the third was closely related to earlier H1N1 sequences).
Thus, it is unclear if the recent seasonal H1 isolates represent a re-emergence of Brisbane/59-like sequences, new seasonal H1 sub-clade, or are linked to the recently described reassortants in Argentina, which are pandemic H1N1 with seasonal H1 from 2003. The Argentina isolates are of concern because all 8 gene segments have circulated widely in humans, so the swine isolates could easily jump to humans and would register as seasonal H1 in sub-type testing.
However, the majority of influenza A cases reported in the US and worldwide are not sub-typed and confirmation is based on a rapid test which has a notorious low sensitivity, which may be as low as 10% for pandemic H1N1. Thus, the level of H1 may be markedly higher than lab confirmed levels because samples that were false negatives due to the rapid test would not be characterized further by sub-type or antigenic analysis.
The dramatic jump in seasonal H1N1 in week 42 should be addressed with sequence and antigenic analysis. A re-emergence of Brisbane/59 would significantly increase the level of Tamiflu resistance (H274Y) due to prior fixing, while a jump of swine H1 reassortants to humans would signal a new or rapidly evolving H1 pandemic with multiple co-circulating lineages.
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