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Paradigm Shift Intervention Monitoring
Comments On Maryland Death Cluster
The above CDC comments on the H3N2 death cluster in Maryland are curious. The cluster was reported shortly after the CDC week 8 FluView revealed a dramatic spike in H3N2 low reactors. At the time the CDC had released 22 H3N2 sequences from samples collected in 2012, and none were designated as “low reactors”.
However, recently the CDC updated antigenic characterization data on seven of the isolates, which were designated as low reactors, and five of the seven (A/Alabama/02/2012, A/North Carolina/01/2012, A/South Carolina/03/2012, A/Oregon/01/2012, A/South Dakota/02/2012) mapped to the same sub-clade. Moreover, 10 additional isolates (A/Georgia/01/2012, Idaho/02/2012, A/Iowa/01/2012, A/Nebraska/01/2012, A/Nevada/01/2012, A/South Carolina/01/2012, A/Utah/04/2012, A/Vermont/01/2012, A/Virginia/01/2012, A/Washington01/2012 which were not characterized anigenically, phylogenetically mapped into the same sub-clade as the five isolates above indicating the vast majority of 2012 H3N2 isolates in the United States were low reactors.
The CDC has not released the sequences from the Maryland cluster, but it seems likely that these isolates will be low reactors and have the receptor binding domain change V223I, which was present in the sub-clade with most of the recent low reactors (see list here), which includes A/South Carolina/01/2012, which has acquired multiple H3N2v polymorphisms and the new 2012/2013 H3N2 vaccine target A/Victoria/361/2011.
Therefore, release of the sequences would be important for the clarification of the curious comments by the CDC above.