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Commentary
Butler H3N2v Confirmed
Cluster Grows To Fourteen
Recombinomics
Commentary 15:15
August 7, 2012
One case is now confirmed in Clark County as a result of exposure at the Ohio State Fair.
Luckily, none of the illnesses required hospitalization. The victims range in age from three to 36-years old.
The above comments cite the four additional confirmed cases at the Butler County Fair in Hamilton as noted in the August 6 press release by the Ohio Department of Health (ODH). However, earlier reports cited 31 symptomatic cases in addition to 10 confirmed cases, so the number of confirmed cases at the fair may continue to rise. Samples are initially tested by the ODH and suspect samples are then sent to the CDC for confirmation, so there may be considerable lag between symptoms and the announcement of confirmation.
The CDC has released sequences for one of the cases, A/Ohio/13/2012 and like all other sequences reported in 2012 the case represented a novel H3N2v that was first seen at a West Virginia day care center in late 2011(A/West Virginia/06/2011 and A/West Virginia/07/2011) . Like the first 10 H3N2v cases in 2011, the sequence has an H1N1pdm09 M gene, but the N2 gene is from a swine H3N2 lineage instead of an H1N2 lineage seen in initial 2011 human cases. Prior to the outbreak in LaPorte, this novel H3N2 was rarely detected in swine in spite of enhanced testing by the USDA, which has identified 24 swine matches for the earlier sequences from 2011, but only two matches (A/swine/North Carolina/A01203272/2012 and A/swine/Indiana/A01203509/2012) with the 2012 human cases.
This novel sub-clade has been linked to several large clusters and transmits human to human, media myths notwithstanding. There were two confirmed cases at the West Virginia day care center, but an alert from the California Department of Public Health noted that 23 contacts of the index case had influenza-like illness at a time when no confirmed cases had been detected in West Virginia. The two H3N2v cases were the first two influenza cases reported in West Virginia for the 2011/2012 season.
In the LaPorte outbreak, 4 or 5 cases were confirmed, but 15 symptomatic cases linked to the fair were identified. Similarly, the Butler County Fair had over two dozen symptomatic cases in addition to the 14 confirmed cases. There have also been 4 or 5 confirmed cases at the Jackson County Fair, but testing is still ongoing. Similarly, clusters of confirmed or suspect cases are linked to the Monroe County and Washington County Fairs.
Although media reports have assumed that the human cases were infected by the pigs, it is well known that swine influenza in humans can jump back to pigs, and the large number of infected pigs at the fairs may be linked to human cases such as the symptomatic cases seen in Jackson in the six weeks prior to the start of the fair.
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