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Commentary
H3N2v Ohio
Cases Increase to 47 in 11 Counties
Recombinomics
Commentary 23:15
August 13, 2012
The above list represents the August 13 tally of H3N2v cases confirmed in Ohio by the Ohio Department of Health (ODH). The number of cases increased from 36 to 47, while the number of counties increased from 8 to 11. This tally demonstrates that H3N2v is widespread in Ohio, but the numbers reflect a small fraction of the cases in each county. Butler still has the largest number of confirmed cases, but Gallia has increased to double digits.
However, in Gallia County the first 200 symptomatic cases were tested, and 60 were influenza A positive by a commercial raid test (which was not included in the CDC analysis of commercial test kits described in Friday’s MMWR. The 200 tested cases in Galiia represented a sub-set of those with symptoms, and only a sub-set of the 69 influenza A positive cases was forward to ODH for confirmation.
The update list above also includes the first three presumptive positive cases in Champaign County, where 5 additional cases had been cited last week, as officials told residents not to seek medical attention if not at risk (and symptoms are mild). Thus, only a tiny fraction of the cases in Champaign County will be tested.
Although these cases were tested under the CDC off seasonal surveillance system of ILI cases with swine exposure, there is little data to support infection of these cases by H3N2v from swine. All human 2012 reported to date have a novel H3N2v with an N2 from a lineage first reported at a West Virginia day care center in November and December of 2011. The H3N2v sub-clade detected in the first 10 cases in 2011 are widespread and was detected in four June, 2012 isolates from Ohio (A/swine/Ohio/1/2012, A/swine/Ohio/6/2012, A/swine/Ohio/7,2012 A/swine/Ohio/9/2012), yet this sub-clade has not been detected in any of the human 2012 cases. The last human case with this sub-clade was in November, 2011 in Iowa.
Thus, the H3N2v has evolved into a virus that more efficiently infects humans. The CDC issued a warning in December, 2011 when an epidemiological study of the West Virginia outbreak identified ILI in 23 of the 70 contacts of the index case (patient zero). All human cases since this outbreak have matched this novel constellation, which the CDC has yet to announce.
The expanded number of counties in Ohio, parallels results from Indiana, where the CDC program continues to identify new cases in new counties, highlighting the need for aggressive testing of ILI cases throughout the United States, which have no swine contact. All recent US H3N2 cases (July collections) are H3N2v. There are sequences from only one June isolate (which is seasonal H3N2 from an adult, 60F, in Utah.
The lack of testing in cases with no swine contact, such as the ILI cases in Jackson County in Indiana for the six weeks prior to the recent series of July cases, continues to be hazardous to the world’s health.
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