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Commentary
Laporte and
Butler County H3N2v
Sequences Match
Recombinomics
Commentary 22:00
August 2, 2012
Although the H3N2v sequences from the above confirmed cases at the Butler County Fair in Hamilton, Ohio have not yet been made public, two full sets of sequences from the LaPorte County Fair were released by the CDC last week (A/Indiana/07/2012 and A/Indiana/09/2012). The two sequences from Indiana exactly matched each other and were closely related two the two sets of sequences from an outbreak at a West Virginia daycare center in Mineral County. Two cases were confirmed (A/West Virginia/06/2011 and A/West Virginia/07/2011).
70 contacts of the index case were surveyed and 23 had influenza-like illness (ILI). The two confirmed cases had no swine contact or exposure and the H3N2v was circulating at the day care center for a month, clearly demonstrating sustained human to human transmission, CDC denials notwithstanding.
The West Virginia sequences were novel and distinct from the fist 10 human cases in 2011 due to an N2 that matched a lineage in H3N2 swine, in contrast to the N2 in the earlier cases which match N2 circulating H1N2 swine. This novel sub-clade also was involved in the first 2012 case, A/Utah/10/2012, and all confirmed cases in LaPorte and Butler counties based on the two sets of released sequences and CDC statements on matches.
The LaPorte 4 confirmed H3N2v cases represented the largest confirmed cluster reported to date. There were also 15 people linked to the fair who had ILI based on a telephone survey of 130 attendees (this survey is still ongoing). The large number of confirmed and symptomatic case support efficient transmission to humans (from swine or humans).
The 9 or 10 confirmed cases at the Butler County fair eclipsed the LaPorte record. In addition to the 10 cases tested by the CDC, 31 additional people linked to the Butler fair had ILI, again demonstrating efficient H3N2v spread to humans.
It is likely that this same sub-clade will be identified in the Indiana cases from Monroe and Jackson counties, which may surpass the number of confirmed cases in Butler County.
This novel sub-clade is clearly transmitting to humans in Indiana and Ohio, CDC denials of sustained transmission notwithstanding.
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