Influenza A (H3N2) Variant Virus Infections Associated with Agricultural Fair Exposures — Ohio, 2012

Quinn, Celia L

Monday, June 10, 2013: 10:30 AM

Ballroom B (Pasadena Convention Center)

Celia L Quinn , Ohio Department of Health, Columbus, OH

Adena Greenbaum , Centers for Disease Control and Prevention, Atlanta, GA

Fiona Havers , Centers for Disease Control and Prevention, Atlanta, GA

Lizette O Durand , Centers for Disease Control and Prevention, Atlanta, GA

Su Su , Centers for Disease Control and Prevention, Atlanta, GA

Victoria Jiang , Centers for Disease Control and Prevention, Atlanta, GA

Shannon L Page , Ohio Department of Health, Columbus, OH

Brian Fowler , Ohio Department of Health, Columbus, OH

Richard Thomas , Ohio Department of Health, Columbus, OH

Michael Jhung , Centers for Disease Control and Prevention, Atlanta, GA

Mary Diorio , Ohio Department of Health, Columbus, OH

Elizabeth Conrey , Ohio Department of Health, Columbus, OH

Edward Weiss , Centers for Disease Control and Prevention, Atlanta, GA

BACKGROUND:

The first 12 human cases of influenza A (H3N2) variant virus (H3N2v) infection, a swine-origin virus, were detected in 2011. The H3N2v virus contains a 2009 (H1N1) pandemic virus gene that might enhance human-to-human transmission. We investigated reports of H3N2v in Ohio and assessed risk factors for influenza-like illness (ILI) among swine exhibitors at an agricultural fair with confirmed illness.

METHODS:

Local health districts identified persons for polymerase chain reaction (PCR) testing who had ILI and were hospitalized or reported swine exposure. We reviewed reports of PCR-confirmed H3N2v among Ohio residents with illness onsets during July–September 2012. We interviewed swine exhibitors and household members (Cohort X) at one fair and used multivariable logistic regression to identify risk factors for ILI.

RESULTS:

We identified 107 confirmed H3N2v cases, including six in Cohort X. Median age was 6 years (range: <1–61 years); 11 (10%) were hospitalized; one died. Three patients denied swine exposure, and eight experienced symptom onset ≥4 days after exposure. Among Cohort X (swine exhibitors, N=150; total, N=359), 45 persons (12.5%) had ILI. Exhibitors and household members reported similar swine exposures. ILI was more common among children aged <10 years versus ≥10 years (relative risk [RR]: 3.94; 95% confidence interval [CI]: 2.3–6.5) and persons who spent >4 hours/day in the swine barn versus ≤4 hours (RR: 1.7; CI: 1.004–2.9), adjusted for underlying medical conditions.

CONCLUSIONS:

Eleven H3N2v virus infections occurred among persons with no swine exposure or symptom onset outside the expected incubation period, prompting suspicion for limited human-to-human transmission. For swine exhibitors, the risk for ILI was higher among children and increased with time in the swine barn.