Wisconsin and Pennsylvania H3N2v Match WV Sub-Clade
August 25, 2012
The CDC has released 8 more sets of H3N2v sequences (at GISAID). Six of the sequences are from Indiana samples collected in late July (A/Indiana/14/2012 and A/Indiana/16/2012) or early August (A/Indiana/43/23012, A/Indiana/46/23012, A/Indiana/49/23012, A/Indiana/52/23012). One sample is from Wisconsin (A/Wisconsin/22/2012 collected August 13) and one from Pennsylvania (A/Pennsylvania/13/2012 collected August 15). All are closely related to each other and match the sub-clade first reported in the West Virginia day care cluster, which had no swine exposure or contact and 23 of the contacts of the index case had ILI.
This sub-clade has only been reported in 2 swine isolates. In contrast, the H3N2v sub-clade identified in the first 10 cases in 2011 is widespread in 2012 swine isolates, but has caused no reported human cases since the Iowa cluster in November, 2011, casting serious doubt on swine to human transmission as a common mechanism for the reported human infections.